Atomic Structure & The Periodic Table

Question 1

Define an atom.

Answer 1

The smallest particle of an element that retains its chemical properties.

Question 2

Define an element.

Answer 2

A substance made of only one type of atom (e.g.

Question 3

Define a compound.

Answer 3

Two or more elements chemically bonded (e.g.

Question 4

What distinguishes a mixture from a compound?

Answer 4

Mixtures are physically combined; compounds are chemically bonded.

Question 5

Name 4 separation techniques.

Answer 5

Filtration, crystallization, distillation, chromatography

Question 6

When is fractional distillation used?

Answer 6

To separate liquids with similar boiling points (e.g., ethanol/water)

Question 7

What did Rutherford’s alpha scattering experiment show?

Answer 7

Most atoms are empty space; mass is concentrated in a nucleus.

Question 8

Describe Dalton’s atomic model.

Answer 8

Atoms are solid indivisible spheres

Question 9

How did Mendeleev arrange the periodic table?

Answer 9

By atomic weight, leaving gaps for undiscovered elements.

Question 10

Modern periodic table order.

Answer 10

By atomic number (number of protons).

Question 11

Charge/mass of a proton.

Answer 11

+1 charge; mass = 1

Question 12

Charge/mass of a neutron.

Answer 12

0 charge; mass = 1

Question 13

Charge/mass of an electron.

Answer 13

-1 charge; negligible mass (≈1/1836)

Question 14

Atomic number definition.

Answer 14

Number of protons in an atom.

Question 15

Mass number definition.

Answer 15

Protons + neutrons in an atom.

Question 16

Isotopes definition.

Answer 16

Atoms of the same element with different numbers of neutrons.

Question 17

Calculate relative atomic mass (Aᵣ).

Answer 17

Aᵣ = (isotope1 × %1) + (isotope2 × %2) / 100 (e.g., Cl: 35.5)

Question 18

Electronic structure of sulfur (atomic number 16).

Answer 18

2,8,6

Question 19

Group number vs. electrons in outer shell.

Answer 19

Group number = number of outer electrons (for Groups 1

Question 20

Period number meaning.

Answer 20

Number of electron shells.

Question 21

Properties of metals.

Answer 21

Conductors, malleable, form positive ions

Question 22

Properties of non-metals.

Answer 22

Poor conductors, brittle, form negative ions

Question 23

Group 0 elements name and reactivity.

Answer 23

Noble gases; unreactive (full outer shell)

Question 24

Trend in noble gas boiling points.

Answer 24

Increases down the group (doesn’t take a lot of energy to overcome the bonds, as it neither gains nor loses electrons)

Question 25

Group 1 trend in reactivity.

Answer 25

Increases down the group (outer electron further from nucleus)

Question 26

Reaction: Sodium + water.

Answer 26

Sodium hydroxide + hydrogen (2Na + 2H₂O → 2NaOH + H₂)

Question 27

Physical property of alkali metals.

Answer 27

Soft, low density (e.g., Li floats on water)

Question 28

Group 7 name and reactivity trend.

Answer 28

Halogens; reactivity decreases down the group (the attraction between the nucleus and the electron shells weakens as the atomic size increases.)

Question 29

Trend in halogen MP/BP.

Answer 29

Increases down the group: As molecular mass increases down the group, it takes more energy to overcome the intermolecular forces.

Question 30

Rf value formula.

Answer 30

Rf = distance moved by substance / distance moved by solvent.

Question 31

Purpose of chromatography.

Answer 31

Separate mixtures based on solubility in a solvent.

Question 32

Why did Mendeleev leave gaps?

Answer 32

To predict undiscovered elements (e.g., gallium)

Question 33

Why do isotopes have identical chemical properties?

Answer 33

Same number of electrons/protons; different neutrons affect physical properties only.

Question 34

Why are Group 1 metals stored in oil?

Answer 34

To prevent reaction with oxygen/water

Question 35

Observation when chlorine displaces bromine.

Answer 35

Solution turns orange (Br₂ forms).

Question 36

Explain Group 7 displacement reactions.

Answer 36

More reactive halogens oxidize less reactive halide ions