8.3- MORE TRENDS IN PROPERTIES OF THE ELEMENTS OF PERIOD 3

Question 1

What does the atomic radii tell us about the atom?

Answer 1

size of atom

Question 2

Can you measure the radius of an isolated atom?

Answer 2

no

Question 3

Why can’t you measure the radius of an isolated atom?

Answer 3

as there is no clear point at which the electron cloud density around it drops to zero

Question 4

What is used to measure the radius of an atom?

Answer 4

half the distance between the centres of a pair of atoms

Question 5

What does the atomic radius of an element depend on?

Answer 5

type of bond it’s forming- covalent, ionic, metallic, van der Waals + so on

Question 6

What radius is most commonly used as a measure of the size of the atom?

Answer 6

covalent radius

Question 7

Can metals form covalent molecules?

Answer 7

yes

Question 8

Example of metal that can form covalent molecules?

Answer 8

Na2, in gas phase

Question 9

Do noble gases bond covalently?

Answer 9

no

Question 10

What sort of property is atomic radius?

Answer 10

periodic property

Question 11

Why is atomic radius a periodic property?

Answer 11

as it decreases across each period + there’s a jump when starting the next period

Question 12

What happens to the size of the atom going down a group?

Answer 12

atoms get larger down any group

Question 13

Why does the radii of atoms decrease across a period? (5)

Answer 13

across period, adding protons to nucleus + electrons to outer main level
charge on nucleus increases
increased charge pulls electrons in closer to nucleus
no additional electron shells to provide more shielding
so size of atom decreases

Question 14

Why does the radii of atoms increase down a group? (2)

Answer 14

atoms of each element have one extra complete main level of electrons compared with one before
so outer electron main level further from nucleus + atomic radii increase

Question 15

What is the first ionisation energy?

Answer 15

energy required to convert a mole of isolated gaseous atoms into a mole of singly positively charged gaseous ions, that is, to remove one electron from each atom

Question 16

What pattern does the first ionisation energies have?

Answer 16

periodic pattern

Question 17

How does first ionisation energy generally change across a period?

Answer 17

generally increases across a period

Question 18

How does first ionisation energy change going down a group?

Answer 18

decreases going down a group

Question 19

Why does the first ionisation energy increase across a period? (2)

Answer 19

number of protons in nucleus increases but electrons enter same main level
increased charge on nucleus means it gets increasingly difficult to remove an electron

Question 20

Why does the first ionisation energy decrease going down a group? (4)

Answer 20

number of filled inner levels increases down a group
results in increase in shielding
electron to be removed at increasing distance from nucleus + so held less strongly
so outer electrons get easier to remove going down a group as they’re further away from nucleus

Question 21

Why is there a drop in ionisation energy from one period to the next?

Answer 21

a new main level starts + so there’s increase in atomic radius, the outer electron’s further from nucleus, less strongly attracted + easier to remove