Periodic Table Quiz - Answer Key

Section A Groups and Element Families - Answers

Problem 1

Alkali Metals group:

a. Group 1

Alkali metals: Li, Na, K, Rb, Cs, Fr (all in Group 1)
Note: Hydrogen is in Group 1 but is NOT an alkali metal.

Problem 2

Least reactive elements:

d. Noble Gases

Noble gases (Group 18) have full outer shells, making them extremely stable and unreactive.

Problem 3

NOT a noble gas:

a. Ra (Radium)

Ra (Radium) is in Group 2 - an alkaline earth metal.
Don't confuse with Rn (Radon), which IS a noble gas!

Noble gases: He, Ne, Ar, Kr, Xe, Rn (all Group 18)

Problem 4

Match groups to families:

a. Group 1 = Alkali Metals
b. Group 2 = Alkaline Earth Metals
c. Group 17 = Halogens
d. Group 18 = Noble Gases

Problem 5

Lanthanides and actinides:

d. filling in f level electrons

Lanthanides fill the 4f sublevel
Actinides fill the 5f sublevel
Together they make up the f-block of the periodic table.

Section B Periodic Table Blocks - Answers

Problem 6

Groups 13-18 are filling:

a. p sublevels

Groups 13-18 = the p-block
Elements here are filling their p sublevels (np¹ through np⁶)
The s electrons were already filled before p starts.

Problem 7

Block identification:

a. Ca = s-block (Group 2)
b. Cl = p-block (Group 17)
c. Fe = d-block (transition metal)
d. U = f-block (actinide)

Problem 8

Transition metals block:

c. d-block

Transition metals (Groups 3-12) are filling d sublevels.

Section C Periodic Trends - Answers

Problem 9

Smallest atomic radius in Group 15:

d. N (Nitrogen)

Atomic radius DECREASES going UP a group.
N is at the top of Group 15, so it's the smallest.
Order: Bi > As > P > N (largest to smallest)

Problem 10

Most metallic in Group 14:

d. Sn (Tin)

Metallic character INCREASES going DOWN a group.
Sn is the lowest of the options given.
Order: C < Si < Ge < Sn (least to most metallic)
(Pb would be even more metallic)

Problem 11

Larger atomic radius:

a. Na (left of Cl in same period)
b. K (below Li in same group)
c. S (below O in same group)

Rules applied:
- Radius increases going LEFT across period
- Radius increases going DOWN a group

Problem 12

Atomic radius across a period:

b. decreases

More protons = stronger pull on electrons = smaller atom
Electrons are added to the same energy level, so the increased nuclear charge pulls them closer.

Problem 13

Metallic character down a group:

a. increases

Going down, atoms are larger and electrons are farther from the nucleus.
This makes it easier to lose electrons, which is characteristic of metals.

Section D Metals, Nonmetals, and Metalloids - Answers

Problem 14

Classifications:

a. Na = Metal
b. Si = Metalloid
c. S = Nonmetal
d. Fe = Metal

Na: Group 1 alkali metal
Si: On the staircase line (semiconductor)
S: Group 16, right side of table
Fe: Transition metal

Problem 15

Metals form:

b. Cations (positive ions)

Metals LOSE electrons to form positive ions (cations).
Example: Na → Na⁺ + e⁻

Problem 16

Incorrect formula:

c. AlO

Typical ion charges:
- Na⁺, Cl⁻ → NaCl ✓
- K⁺, O²⁻ → K₂O ✓
- Al³⁺, O²⁻ → should be Al₂O₃, not AlO ✗
- Ba²⁺, O²⁻ → BaO ✓

AlO would require Al⁺², but aluminum typically forms Al³⁺.

Section E Challenge Problems - Answers

Problem 17

Most similar to Ca:

c. Sr (Strontium)

Elements in the SAME GROUP have similar properties.
Ca is in Group 2 (alkaline earth metals).
Sr is also in Group 2, directly below Ca.

K is Group 1, Sc is Group 3, Ga is Group 13.

Problem 18

Increasing atomic radius (O, S, Se, Te):

O < S < Se < Te

All are in Group 16.
Going DOWN a group, atomic radius INCREASES.
O is at top (smallest), Te is at bottom (largest).

Problem 19

Why same group = similar properties:

Elements in the same group have the same number of valence electrons.

Chemical properties depend on how elements interact with other atoms, which is determined by valence electrons.

Example: All alkali metals (Group 1) have 1 valence electron, so they all:
- Form +1 ions
- React violently with water
- Are highly reactive

Problem 20

Predicted ion charges:

a. K: +1
b. O: -2
c. Al: +3
d. Br: -1

K (Group 1): loses 1 electron → +1
O (Group 16): gains 2 electrons → -2
Al (Group 13): loses 3 electrons → +3
Br (Group 17): gains 1 electron → -1

Pattern: Metals lose electrons to reach noble gas configuration.
Nonmetals gain electrons to reach noble gas configuration.

Problem 21

Most reactive element:

a. Na (Sodium)

Reactivity comparison:
- Na: Alkali metal (Group 1) - very reactive
- Mg: Alkaline earth (Group 2) - reactive but less than Na
- Al: Group 13 - moderately reactive
- Ar: Noble gas - essentially no reactivity

Alkali metals only need to lose ONE electron to be stable.

Problem 22

2 s electrons + 5 p electrons:

Group 17, Nonmetal