The Periodic Table

Question 1

What are Dobereiner’s triads?

Answer 1

A triad is a group of elements with similar chemical properties in which the atomic weight of the middle elements is approximately halfway between the other two

Question 2

What are Newland’s octaves?

Answer 2

When arranged by atomic weight, the properties of elements seemed to be repeated every eight element

Question 3

What is Mendeleev’s periodic law?

Answer 3

When elements are arranged according to atomic weight, their properties repeat periodically

Question 4

What did Henry Moseley do?

Answer 4

Used x-ray analysis to discover atomic number

Question 5

What is the atomic radius?

Answer 5

Atomic radius is half the distance between two nuclei of identical atoms, joined by a single covalent bond

Question 6

Who gave the first accurate description of an element. State it.

Answer 6

1. Robert Boyle

2. An element is a substance that cannot be split into simpler substances by chemical means

Question 7

What are the trends in the periodic table?

Answer 7

1. Atomic (covalent) radius
2. Ionisation energy
3. Electronegativity

Question 8

Differences between the Mendeleev periodic table and the modern one?

Answer 8

Mendeleev. Modern

1. Arranged by atomic weight. 1. Arranged by atomic no.
2. Gaps for elements. 2. No gaps
3. No group 8. 3. Group 8
4. Transition metals not in 4. Transition metals in
   separate block Separate block

Question 9

What happens to the atomic radius when you go down a group?

Answer 9

It increases

Question 10

What happens to the atomic radius we go across a period?

Answer 10

It decreases

Question 11

What did Humphry Davy do?

Answer 11

1. Studied the effect of passing electricity through different substances
2. Isolated elements K, Na and Ca through electrolysis

Question 12

What is the definition of the modern periodic table?

Answer 12

The modern periodic table is an arrangement of elements in order of increasing atomic number.