This post is about Chemistry Periodic Table Trends (Down Group 1 and 17).
Last week, our post was about Chemistry Periodic Table Trends (Across a Period). This week, it will be about trends (Down Groups 1 and 17).

Trends Down Group 1 (Alkali Metals)

Atomic Size:
Trend: Increases down the group.
Explanation: As you move down Group 1, each element has an additional electron shell, increasing the distance between the nucleus and the outermost electron, making the atoms larger.
Tip: More shells = Bigger atoms!

Reactivity:
Trend: Increases down the group.
Explanation: The outer electron becomes more easily lost as the atomic size increases. The increased distance between the nucleus and the outer electron weakens the nuclear attraction, making it easier for the metal to lose its electron and react.
Tip: Easier to lose electrons, more reactive!

Ionization Energy:
Definition: Ionization energy is the energy required to remove 1 electron from an atom.
Trend: Decreases down the group.
Explanation: Since the outer electron is farther from the nucleus, it is held less tightly. Therefore, less energy is required to remove the outer electron.
Tip: Farther electrons are easier to remove!

Melting and Boiling Points:
Trend: Decrease down the group.
Explanation: The atoms are larger and the metallic bonds between the atoms become weaker, requiring less energy to break the bonds.
Tip: Weaker bonds = Lower melting and boiling points!
Trends Down Group 17 (Halogens)

Atomic Size:
Trend: Increases down the group.
Explanation: Like Group 1, as you move down Group 17, the number of electron shells increases, making the atomic radius larger.
Tip: More shells = Bigger atoms!

Reactivity:
Trend: Decreases down the group.
Explanation: Halogens react by gaining an electron. As the atomic size increases, the nuclear attraction for an extra electron decreases, making it harder for the halogen to gain an electron.
Tip: Bigger atoms = Harder to gain electrons!

Electronegativity:
Definition: Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond.
Trend: Decreases down the group.
Explanation: The increased atomic size down the group means the outer electrons are farther from the nucleus, resulting in a weaker attraction for bonding electrons.
Tip: Bigger atoms attract bonding electrons less!

Melting and Boiling Points:
Trend: Increase down the group.
Explanation: The size of the halogen molecules increases, leading to stronger Van Der Waals (Intermolecular) forces between molecules, which require more energy to overcome.
Tip: Bigger molecules = Stronger forces = Higher melting and boiling points!

In summary:
Group 1 metals become more reactive as you go down, with decreasing ionization energy and lower melting/boiling points.
Group 17 elements become less reactive, with decreasing electronegativity but increasing melting/boiling points due to stronger intermolecular forces.
Finished!
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