Chemistry Unit Test: Periodic Trends

Questions and Answers

Describe the trend in atomic radius as the atomic number increases across a period.

As the atomic number increases, the radius decreases.

Describe the trend in the atomic radius as the atomic number increases down a group.

Atomic radius increases as you go down.

Explain why the radius increases going down a group and decreases going across a period.

Radius increases down a group due to electron shielding as electrons are further from protons. It decreases across a period due to increased positive nuclear charge pulling electrons closer.

Define 'first ionization energy'.

Energy needed to remove an electron from the outer energy level of an atom. Signup and view all the answers

Describe the overall trend in ionization energy as the atomic number increases across a period.

As the atomic number increases, the ionization energy increases. Signup and view all the answers

Describe the overall trend in ionization energy as the atomic number increases down a group.

As you go down a group, the ionization energy decreases. Signup and view all the answers

Define 'electronegativity'.

An atom's ability to attract electrons from other atoms. Signup and view all the answers

Describe the trend in electronegativity as the atomic number increases across a period.

Electronegativity increases across the period, not including noble gases. Signup and view all the answers

Describe the trend in electronegativity as the atomic number increases down a group.

Electronegativity decreases as you go down a group. Signup and view all the answers

Why do you think the electronegativity of He, Ne, and Ar is 0?

They are noble gases and have a full shell. Signup and view all the answers

Study Notes

Atomic Radius Trends

Atomic radius decreases across a period as atomic number increases.
Atomic radius increases down a group for alkali and alkaline earth metals due to additional electron shells.

Explanation of Atomic Radius Behavior

Increase down a group: Electrons are farther from the nucleus, resulting in reduced pull due to electron shielding.
Decrease across a period: Adding protons increases positive nuclear charge, which pulls electrons closer, reducing atomic radius.

Ionization Energy

First ionization energy is the energy required to remove an electron from an atom's outermost energy level.
Ionization energy increases across a period with increasing atomic number due to stronger positive charge attracting electrons.
Ionization energy decreases down a group as the outer electrons are farther from the nucleus, requiring less energy to remove.

Electronegativity

Electronegativity is the ability of an atom to attract electrons from other atoms.
Electronegativity increases across a period, excluding noble gases.
Electronegativity decreases down a group as the distance from the nucleus to the outer electrons increases.

Noble Gases and Electronegativity

Helium (He), Neon (Ne), and Argon (Ar) have an electronegativity of 0 because they possess a complete electron shell, making them chemically inert.

Description

Test your knowledge on atomic radius trends in the periodic table with this quiz. Explore how atomic radius changes across periods and down groups, and understand the underlying reasons for these trends. Perfect for students preparing for chemistry assessments!