L3: The Periodic Table of the Elements

Question 1

What is “the single mass of a single atom; the total mass of the protons, neutrons, and electrons”?

Answer 1

Atomic mass

Question 2

What is “the total number of protons and neutrons in the nucleus”?

Answer 2

Mass number

Question 3

What is “the number that identifies an element and is the total number of protons in the nucleus”?

Answer 3

Atomic or proton number

Question 4

What did Dobereiner theorise?

Answer 4

The law of triads. He noticed a pattern that if you took a certain triad, the average of their collective weights would equal the weight of the middle element.

e.g.
Cl, Br, I - 35.5, 80, 127
Li, Na, K - 7, 23, 39
Ca, Sr, Ba - 40, 88, 137

Question 5

Which side of the table is dominated by non-metals?

Answer 5

Right side

Question 6

What is the formal statement of the Periodic Law?

Answer 6

“Properties of elements are periodic functions of their atomic numbers.”

Question 7

True or false: The most reactive metals are further down the group

Answer 7

True

Question 8

True or false: Atoms get smaller further down the group

Answer 8

False. Atoms increase in size down a group

Question 9

True or false: Metals become more reactive down the group, but non-metals become less reactive

Answer 9

True

Question 10

What is an empirical formula?

Answer 10

The simplest ratio of the elements on a molecule.

E.g.
H2O = H2O
H2O2 = HO
C6H12O6 = CH2O

Question 11

What are the steps to calculating an empirical formula based on % mass?

Answer 11

1) Write out the % mass of each element
2) Divide the % mass by the element’s relative atomic mass
3) Divide each by the smallest number

Question 12

What are the steps to calculate % composition from a formula? (e.g. find the % of iron in FeSO4.7H2O)

Answer 12

1) Calculate the relative molecular mass by totalling the atomic mass of each constituent atom
2) Divide the Ar of iron by the Mr and times by 100