Chemistry - Course

Question 1

Define atoms.

Answer 1

Building blocks of the universe; the smallest particle of a chemical that can exist.

Question 2

Define elements.

Answer 2

A substance whose atoms all have the same number of protons. Elements are chemically the simplest substances and cannot be broken down.

Question 3

Define atomic number.

Answer 3

The number of protons in the nucleus of an atom.

Question 4

Define mass number.

Answer 4

The total number of protons and neutrons in a nucleus.

Question 5

What are all the components of an atom?

Answer 5

• Subatomic particles -> protons, neutrons, and electrons.
• Nuclues -> protons and neutrons
• Electron cloud/shell -> electrons

Question 6

Define an isotope.

Answer 6

An element/atom that contains the same number of protons, but a different number of neutrons.

Question 7

Why do some elements have a decimal as a mass number?

Answer 7

Because most elements have isotopes (varying number of neutrons). The decimal is an average of the various isotopes of an element, taking into account how common some isotopes are to others.

Question 8

Define the periodic table of elements.

Answer 8

A tabular display of the chemical elements arranged by atomic number, electron configuration, and recurring chemical properties.

Question 9

Define groups.

Answer 9

Columns of the periodic table which identify the number of valence electrons and reactivity.

Question 10

Define periods.

Answer 10

Horizontal rows of the periodic table which identify the number of shells that the element has.

Question 11

What is the full electron shell configuration (for 3 shells)?

Answer 11

2 . 8 . 8

Question 12

List the metal reactivity series.

Answer 12

Phosphorous, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, nickel, tin, lead, hydrogen, copper, mercury, silver, gold, platinum.

Question 13

What happens to an atom once it loses an electron?

Answer 13

It has been oxidised to form a cation.

Question 14

Define cation.

Answer 14

A positively charged ion.

Question 15

What happens to an atom once it gains an electron?

Answer 15

It has been reduced to form an anion.

Question 16

Define anion.

Answer 16

A negatively charged ion.

Question 17

Do metals form cations or anions?

Answer 17

Sine metals always have low numbers of electrons, they will always be oxidised to form a cation.

Question 18

Do non-metals form cations or anions?

Answer 18

Since non-metals have higher numbers of electrons in their valence shells, they tend to gain electrons, reduced to form anions.

Question 19

Why do elements form ions when they react with other substances?

Answer 19

Because all elements want to be stable and become isoelectric with noble gases by losing/gaining the appropriate number of electrons to fill their valence shells.

Question 20

What is group 1 referred to as?

Answer 20

Alkali metals.

Question 21

What are the properties of alkali metals?

Answer 21

• soft and silver
• low ionization energy
• low melting points
• highly reactive
• not found in their elemental forms in nature
• noted for how vigorously they react with water.

Question 22

What is group 2 referred to as?

Answer 22

Alkaline earth metals.

Question 23

What are the properties of alkaline earth metals?

Answer 23

• naturally occurring
• quite reactive
• silver and soft
• react with water (except beryllium) but not as vigorously as group 1.

Question 24

What is group 17 referred to as?

Answer 24

Hallogens.

Question 25

What are the properties of hallogens?

Answer 25

• non metals
• compounds containing hallogens are called ‘salts’
• 7 valence electrons.

Question 26

What is group 18 referred to as?

Answer 26

Noble/inert gases.

Question 27

What are the properties of noble gases?

Answer 27

• full shell configuration (stable)
• very low reactivitiy
• gases - colourless, odorless
• extremely rare in nature.

Question 28

What is atomic radius and how is it measured?

Answer 28

The size of an atom is measure from the nucleus to the outer shell.

Question 29

What is the trend of the atomic radius and why is it so?

Answer 29

• As you move down a group, atomic radius increases because there are more electrons shells, and all the extra electrons reduce the effect of core charge due to electron-electron repulsion known as ‘shielding’. The force pulling the valence electrons in are weaker than ones in previous periods, and so atomic size is bigger.
• As you move across the same period the atomic radius decreases. This is because the core charge increases, therefore the valence electrons are being pulled closer to the nucleus, making the size of the atom smaller.

Question 30

What is core charge and how is it calculated?

Answer 30

• The attractive force of the nucleus of an atom on the valence electrons.
• calculated by taking the number of protons of an atom and subtracting the number of inner-shell electrons. You should always get a positive value.

Question 31

What is the trend of the core charge?

Answer 31

• Core charge increases across a period.

- Core charge stays the same down a group.

Question 32

What is ionization energy?

Answer 32

The energy required to take away a valence electron.

Question 33

What is the trend of ionization energy?

Answer 33

• ionization energy increases as you go from metals to non-metals because the core charge increases in the same direction (valence electrons are held tighter for non-metals than metals), therefore more energy is required to remove electrons.
• as you go down a group, ionization energy decreases because at the bottom valence electrons are not as effected by core change.

Question 34

What is ionic radius?

Answer 34

The radius of ions rather than the neutral atom.

Question 35

What is the ionic radius trend?

Answer 35

• cations are smaller, anions are larger
• in cations there are less electrons involved in repelling other electrons therefore shielding effect is less, and core charge effect is greater, thus pulling electrons in tighter making the radius smaller.
• in anions, more electrons increase the shielding effect, which decreases the effective core charge, therefore the electrons are held less tighter, effectively increasing the radius.
• in simpler terms, as you go across a period, ionic size decreases, and as you go down a group, the ionic radius decreases.

Question 36

What is metallic character?

Answer 36

Refers to the level of reactivity of a metal. Metals tend to lose electrons in chemical reactions, as indicated by their low ionization energies.

Question 37

What is the trend of metallic character?

Answer 37

• decreases as you move across a period
• increases as you move down an element group
• this is because of ionization energy (trend is essentially the opposite of this).

Question 38

State the law of conservation of mass.

Answer 38

Mass can be neither created nor destroyed.