Periodic Trends — Drills · Grade 11 Science

Chapter: Atoms, Electrons & Periodicity

What these drills covers

By the end of Periodic Trends you should be able to:

6 questions, multiple choice, written answer and numeric, each with a worked explanation.

Vocabulary used: atomic radius, ionization energy, electronegativity, effective nuclear charge (Zeff), shielding (screening), periodic trend.

Problem 1

As you move down a group, atomic radius generally…
  1. decreases
  2. stays the same
  3. drops to zero
  4. increases
Answer and explanation

increases

Each step down a group adds an energy level, so the outer electrons sit farther out and the atom is larger.

Problem 2

Within the same period, which element has the smaller atomic radius: one on the far left or one on the far right?
  1. the one on the far right
  2. they are the same
  3. it cannot be determined
  4. the one on the far left
Answer and explanation

the one on the far right

Radius decreases across a period, so the element on the far right is smaller.

Problem 3

Which has the higher first ionization energy, lithium (Li) or fluorine (F)? (Both are in Period 2.)
  1. lithium
  2. fluorine
  3. they are equal
  4. neither can be ionized
Answer and explanation

fluorine

Ionization energy increases across a period, so fluorine (far right) holds its electrons more tightly than lithium.

Problem 4

Which is the most electronegative of the halogens chlorine (Cl), bromine (Br), and iodine (I)?
  1. they are identical
  2. chlorine
  3. bromine
  4. iodine
Answer and explanation

chlorine

Electronegativity decreases down a group, so chlorine (highest in the group) is the most electronegative of the three.

Problem 5

Explain why first ionization energy decreases as you move down a group.
Answer and explanation

Going down a group, each element has an additional energy level, so the outermost electron is farther from the nucleus and better shielded by inner electrons. It is held less tightly, so less energy is needed to remove it.

Problem 6

A neutral oxygen atom has 8 protons and 2 core (inner-shell) electrons. Using Zeff ≈ (protons) − (core electrons), estimate the effective nuclear charge felt by a valence electron.
Answer and explanation

6

Zeff ≈ 8 − 2 = 6, a strong pull that helps make oxygen small and highly electronegative.

Browse all courses