Fundamental ideas in chemistry

Question 1

What is the nucleus?

Answer 1

• Middle of an atom
• Contains protons and neutrons
• Has a positive charge due to protons

Question 2

What charge are protons?

Answer 2

Positive

Question 3

What charge are neutrons?

Answer 3

Don’t have a charge

Question 4

What are electrons?

Answer 4

• Move around the nucleus
• Negative charge
• Tiny
• Occupy shells around the nucleus

Question 5

What charge does an atom have overall?

Answer 5

No charge!
( The charge on electrons is the same size as those on protons but opposite; the number of protons always equals the number of electrons in an atom)

Question 6

What is an ion?

Answer 6

When an atom loses or gains electrons, giving it a charge

Question 7

What is an element?

Answer 7

A substance consisting of one type of atom only

Question 8

What gives the indication for the type of atom it is?

Answer 8

The proton number- the number of protons in the nucleus

Question 9

How many elements are there (roughly)?

Answer 9

100

Question 10

What is an atom?

Answer 10

A cluster of sub-particles (protons, neutrons,electrons) which cannot be divided; the smallest part of an element which retains its chemical properties

Question 11

What force holds the sub-particles together in the nucleus?

Answer 11

The “strong force”

Question 12

What are the atomic mass units of each sub-particle?

Answer 12

• Proton = 1
• Neutron = 1
• Electron = 0 (negligible mass)

Question 13

What are the vertical columns of the periodic table and what do they tell us?

Answer 13

Groups: define element groups, same outer shell electron arrangement- this is why elements in the same group have similar properties

Question 14

What are periods in the periodic table; what do they tell us?

Answer 14

Signifies the highest un-exited energy level for an electron in that element

Question 15

What are the different groups of the periodic table? (Generally)Most reactive to least reactive

Answer 15

1- Alkali metals e.g. sodium, potassium
2- Alkali earth metals e.g. magnesium, calcium
- Transition elements- e.g. most metals, iron, copper
3,4,5,6- Non-metals e.g. nitrogen, oxygen
7- Halogens e.g. fluorine, chlorine
0- Noble gases e.g. helium, argon

Question 16

What does inert mean?

Answer 16

Something that isn’t readily reactive with other elements, forming few or no chemical compounds (inactive)

Question 17

Why are the noble gases inert?

Answer 17

Their outer electron shells are already “full” (the more empty an outer shells is, the more reactive it is)

Question 18

e.g. why is potassium more reactive than lithium?

Answer 18

• Both need to lose an electron to have full outer shells

- Potassium has more shells away from positive attraction of the nucleus making it more reactive

Question 19

e.g. why is sodium more reactive than magnesium?

Answer 19

• Sodium must lose one electron to have a full outer shell
• Magnesium must lose two electrons to have a full outer shell
• The latter takes more energy meaning sodium is more volatile and reactive

Question 20

What are the 5 rules about electron shells?

Answer 20

1- Electrons always occupy shells (energy levels)
2- The lowest energy levels are always filled first from closest to the nucleus out
3- Only a certain number of electrons can occupy each cell
4- Atoms are happier when they have full electron shells
5- In most atoms the outer shell is not full meaning that the atom will ‘want’ a reaction to take place to fill it

Question 21

How many electrons are allowed in each shell?

Answer 21

1- 2
2- 8
3- 8

Question 22

What are the two ways of bonding atoms?

Answer 22

Ionic and covalent

Question 23

What does making bonds between atoms involve?

Answer 23

• Involves atoms giving away, taking or sharing electrons

- The nuclei is not involved as that would change the element- only electrons

Question 24

What is ionic bonding?

Answer 24

A compound formed from a metal and a non-metal consisting of ions which strongly attract

Question 25

What is covalent bonding?

Answer 25

• 2 non- metals (same or different atoms)
• Both need to gain electrons to form a full outer shell of electrons
• Electrons shared in pairs
• In each shared pair there can be one or more electrons shared

Question 26

What are some examples of ionic and covalent bonding?

Answer 26

Ionic e.g. magnesium oxide, lithium chloride

Covalent e.g. water, oxygen