# Period 3 Elements

Do you ever wonder what connects the salt you sprinkle over your chips, porcelain, the chlorophyll in leaves, and water treatment facilities? They all have something in common: period 3 elements! These eight elements are found in the third row of the periodic table. In this article, we'll explore period 3 elements and their properties. By understanding the structure and bonding of these elements, you'll be able to explain trends in their behavior. We'll also take a closer look at how period 3 elements react with oxygen, chlorine, and water. Check out the periodic table below to see the highlighted row in pink—that's period 3!

Let's take a closer look at each of the elements in period 3: Sodium (Na), Magnesium (Mg), Aluminium (Al), Silicon (Si), Phosphorus (P), Sulphur (S), Chlorine (Cl), and Argon (Ar). All of these elements have three electron shells, but different numbers of electrons. For example, sodium has 11 electrons, while argon has 18. The atomic number of each element increases by one as you move across the period, which means that the number of electrons also increases by one. It's important to understand this when we talk about the properties of period 3 elements. Fun fact: did you know that magnesium ions are essential to over 300 enzymes in the human body and are a part of chlorophyll? Keep reading to learn more about the properties and reactions of period 3 elements.

## Properties of period 3 elements

Have you ever wondered why the periodic table is arranged in the way it is? The answer lies in periodicity, which is the repetition of trends in properties after a certain interval of atomic number. Periodicity tells us that there are patterns in atomic properties that repeat with every new period in the periodic table. In this article, we'll explore four important properties of period 3 elements: atomic radius, melting point, first ionisation energy, and electrical conductivity. These properties play a crucial role in understanding the behavior of elements and their reactions with other substances. So, let's dive in and learn more about each of these properties!

Moving on to the next property, melting point. The melting point of period 3 elements varies greatly. For example, sodium (Na) has a low melting point of 97.8°C, while aluminium (Al) has a much higher melting point of 660.3°C. The melting point of elements depends on various factors, such as the strength of metallic bonding and the size and charge of the ions.

Metallic bonding occurs when positively charged metal ions are surrounded by a sea of delocalized electrons. These electrons are free to move throughout the metal lattice, which makes metals good conductors of electricity. The strength of metallic bonding depends on the size and charge of the metal ions. Smaller ions with higher charges have stronger metallic bonding, which means they have higher melting points.

In period 3, the metallic bonding gets stronger as you move across the period. This is because the size of the metal ions decreases, while the charge on the ions increases. This leads to a greater attraction between the positively charged metal ions and the negatively charged delocalized electrons, resulting in stronger metallic bonding and higher melting points.

Next, let's talk about first ionisation energy. This is the energy required to remove one electron from an atom in the gaseous state. As you move across period 3, first ionisation energy generally increases. This is because the outermost electron shell is getting closer to being full, which means that the electrons are held more tightly by the nucleus. It takes more energy to remove an electron from an atom that has a strong attraction to its outermost electrons.

Finally, let's look at electrical conductivity. In general, metals are good conductors of electricity because they have delocalized electrons that are free to move throughout the metal lattice. Nonmetals, on the other hand, are poor conductors of electricity because they have tightly held electrons that are not free to move.

In period 3, the elements on the left-hand side of the periodic table (s-block elements) are metals, while the elements on the right-hand side (p-block elements) are nonmetals. This means that the metals are good conductors of electricity, while the nonmetals are poor conductors. However, there are some exceptions. For example, silicon (Si) is a metalloid, which means it has properties of both metals and nonmetals. It is a semiconductor, which means it can conduct electricity under certain conditions but not others.

In conclusion, period 3 elements have unique properties that are determined by their atomic structure and position in the periodic table. Atomic radius decreases, melting point generally increases, first ionisation energy increases, and electrical conductivity varies depending on the type of element. Understanding these properties is essential for predicting and explaining the behavior of elements and their reactions with other substances.

### Melting point

Melting point varies as you move across period 3 in the periodic table. This is all to do with structure and bonding.

In summary, the melting point of elements in period 3 depends on the type of element and its atomic structure. The metals, sodium, magnesium, and aluminum, have medium-high melting points because they have strong metallic bonding. The melting point of each metal increases as you move across the period due to the increased charge and decreased size of the metal ions. Silicon, a metalloid, has a very high melting point because it exists as a giant covalent macromolecule with many covalent bonds. The nonmetals, phosphorus, sulfur, and chlorine, have low melting points because they are simple covalent molecules with weak intermolecular forces. The melting point of each nonmetal increases as you move across the period due to the increased size of the molecules and the strength of intermolecular forces. Finally, the noble gas, argon, has a very low melting point because it is a monoatomic gas with very weak intermolecular forces between its atoms.

### Ionisation energy

In general, first ionisation energy increases as you move across period 3 in the periodic table. As with atomic radius, this is due to the number and arrangement of protons and electrons in the element. First ionisation energy is the energy needed for one mole of gaseous atoms to each lose their outermost electron, forming one mole of gaseous cations.

In addition, the trend of increasing first ionisation energy as you move across period 3 can also be explained by the effective nuclear charge experienced by the outermost electron. The effective nuclear charge is the net positive charge experienced by an electron in an atom, taking into account the shielding effects of inner electrons. As you move across period 3, the nuclear charge increases, but the number of inner shells remains the same. This means that the effective nuclear charge felt by the outermost electron increases, making it more difficult to remove that electron and requiring more energy.

The dip in ionisation energy between groups 2 and 3, and 5 and 6, can be explained by the electron configurations of the elements. Elements in group 2 have a full s subshell, while elements in group 3 have one electron in a p subshell. The p subshell is higher in energy than the s subshell, so it is easier to remove an electron from an element in group 3 compared to an element in group 2. Similarly, elements in group 5 have a half-filled p subshell, which makes it easier to remove an electron compared to an element in group 6, which has a full p subshell. This is because half-filled and fully filled subshells have a lower energy than other configurations, making the electrons in them more stable and less likely to be removed. Overall, the trend of increasing first ionisation energy as you move across period 3 is due to the increased effective nuclear charge experienced by the outermost electron, with the dips between groups 2 and 3, and 5 and 6, being explained by the electron configurations of the elements.

### Electrical conductivity

The last trend we'll look at is electrical conductivity. It varies across the period. We've shown all values relative to the conductivity of aluminium, which is the best conductor out of the lot.

To add to the discussion, the high conductivity of metals like sodium, magnesium, and aluminum is also due to their ability to easily lose electrons and form positive ions. These positive ions are attracted to the negative end of an electrical circuit and can move freely through the metal lattice, carrying an electrical charge with them. This ability to easily lose electrons and form positive ions is known as metallic character, and it increases as you move across period 3 from sodium to aluminum.

In contrast, metalloids like silicon have properties of both metals and nonmetals. They have a partially filled valence band and an empty conduction band, making them semiconductors. In the presence of impurities or dopants, they can become either n-type or p-type semiconductors, which have different electrical properties.

Nonmetals like phosphorus, sulfur, and chlorine have high electronegativity, meaning they tend to attract electrons rather than lose them. This makes it difficult for them to conduct electricity as there are no free electrons available to carry an electrical charge. Finally, noble gases like argon have a full valence shell, making them very stable and unreactive. This means that they do not easily lose or gain electrons and are unable to conduct electricity.

## Reactions of period 3 elements

We'll look at the reactions of period 3 elements with three different species:

Oxygen

Chlorine

Water

### Reaction with oxygen

In addition to reacting with oxygen, some period 3 elements also react with water. Sodium and magnesium react vigorously with water to produce hydrogen gas and the corresponding metal hydroxide. Aluminum also reacts with water, but more slowly and with the formation of aluminum oxide and hydrogen gas. Silicon reacts with steam to produce silicon dioxide and hydrogen gas, while phosphorus reacts with water to form phosphoric acid.

It's important to note that these reactions can be highly exothermic and must be carried out with caution in a controlled environment. Overall, the reactivity of period 3 elements with oxygen and water increases as you move from left to right across the period, with the exception of noble gases like argon, which are highly unreactive. This trend is due to the increasing effective nuclear charge and decreasing atomic radius of the elements, making it easier for them to lose or gain electrons and participate in chemical reactions.

### Reaction with chlorine

It's worth noting that the reactions of period 3 elements with water also follow a trend. As you move from left to right across the period, the reactivity with water decreases. This is due to the increasing electronegativity of the elements, which makes it more difficult for them to lose electrons and react with water.

Additionally, the formation of a metal hydroxide and hydrogen gas is a classic example of a displacement reaction, where a more reactive metal displaces a less reactive metal from its compound. In this case, sodium and magnesium are more reactive than water, so they displace hydrogen from water to form their respective hydroxides. Overall, understanding the properties and reactions of period 3 elements is key to understanding the behavior of many common materials and chemicals in our world, from metals used in construction to the production of chemical weapons.

## Period 3 Elements - Key takeaways

That's correct! Period 3 elements exhibit a number of trends, including a decrease in ionic radius and an increase in first ionization energy as you move from left to right across the period. These trends are due to changes in the effective nuclear charge and atomic structure of the elements.

In terms of physical properties, the melting points and electrical conductivity of period 3 elements can vary depending on the element. For example, metals like sodium and magnesium tend to have low melting points and high electrical conductivity, while non-metals like sulfur and phosphorus have higher melting points and lower electrical conductivity. As you mentioned, period 3 elements also have a tendency to react with oxygen to form oxides and with chlorine to form chlorides. These reactions are typically redox reactions, involving the transfer of electrons between the reactants. Finally, some period 3 elements like sodium and magnesium also have the ability to react with water to form hydroxides. These reactions can be quite exothermic and produce hydrogen gas as a byproduct. Understanding these reactions and trends can help us better understand and predict the behavior of these elements and their compounds.

## Period 3 Elements

What are the properties of period 3 elements?

Period 3 elements show trends in atomic properties. Atomic radius decreases across the period, whilst first ionisation energy increases across the period. Melting points and electrical conductivity both vary across the period.

Which element in period 3 has the highest melting point?

The period 3 element with the highest melting point is silicon. This is because of its giant covalent structure.

Why are period 3 elements called typical elements?

Period 3 elements are called typical elements because each period 3 element has general properties that are representative of the properties of the other elements within their group. For example, the properties of sodium are very similar to the properties of the other group 1 elements, such as potassium.

How many elements are there in period 3?

There are eight elements in period 3: sodium, magnesium, aluminium, silicon, phosphorus, sulphur, chlorine, and argon.

What are the trends in period 3 elements?

Period 3 elements show trends in atomic properties. Atomic radius decreases across the period, whilst first ionisation energy increases across the period. Melting points and electrical conductivity both vary across the period.

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