Periodic Table

Question 1

Why is the periodic table arranged how it is?

Answer 1

So that chemists can understand patterns in the properties of elements

Question 2

How are the elements laid out on the PT?

Answer 2

In order of their Atomic Number

Question 3

What are the main structural features of the periodic table?

Answer 3

Vertical columns called groups and horizontal rows called periods

Question 4

What are some elements along the metal/non-metal divide known as?

Answer 4

Metalloids or semi-metals

Question 5

The sequence and systematic change of properties of elements is known as ______

Answer 5

Periodicity

Question 6

What are the trends of density? (periods 2 and 3)

Answer 6

Increase in density from group 1 to middle of table; Decrease from middle of table to group 8; Density in a group in period 3 elements is higher than in period 2 elements

Question 7

What the the trends of melting points? (periods 2 and 3)

Answer 7

Melting points of: Metals - increase across period and decrease down groups; Non-metals - decrease across periods and increase down groups

Question 8

What are the trends of boiling points? (periods 2 and 3)

Answer 8

Boiling points of: Metals - Increase across period and decrease down groups; Non-metals - decrease across periods and increase down groups (Same as melting points)

Question 9

Define the atomic radius?

Answer 9

Distance between the nucleus and the outermost orbital of an atom

Question 10

What is the ‘true atomic radius?’

Answer 10

Group 8 exist as free atoms

Question 11

What is the ‘covalent radius?’

Answer 11

Diatomic molecules

Question 12

What is the ‘metallic radius?’

Answer 12

Atoms in metallic lattice

Question 13

What are the trends of atomic radiuses?

Answer 13

Increase down a group as extra shell added per period, decrease across a period as increased electrostatic attraction (due to increase of electrons and negative charge) contracts the atom

Question 14

What are halides?

Answer 14

When a halogen reacts with other another element (besides group 8) and form halides

Question 15

Define ionisation energy

Answer 15

The amount of energy required to remove an electron from a gaseous atom to form a cation (positive ion)

Question 16

What happens as ionisation energy gets higher

Answer 16

It becomes more difficult to remove an electron from an atom

Question 17

What are the trends of the first ionisation energy

Answer 17

Ionisation energies increase across a period (extra proton and electron added to atom increasing electrostatic attraction.) Large drop of ionisation energy at the start of each new period (new shell means further from nucleus results in weaker electrostatic forces)

Question 18

Define electron affinity

Answer 18

The energy change when an electron is added to a gaseous atom to form an anion (measure of ability of an atom to accept an electron)

Question 19

What are the trends of electron affinity?

Answer 19

It increases across each period; electron affinities of halogens are highest (by accepting an electron they attain noble gas configuration)

Question 20

Define electronegativity

Answer 20

The ability of an atom in a compound to attract the bonding electron pair(s)

Question 21

What are the trends of electronegativity?

Answer 21

Increase across each period; decreases down a group

Question 22

What is reactivity determined by?

Answer 22

The number of valence electrons that need to be lost or gained to achieve a full outer shell