C4 Flashcards
Give 4 facts about the nucleus of an atom
Charge, location, size, mass, contains
? Positive
? In the middle of the atom
? Contains protons and neutons
? Almost the whole mass of the atom is concentrated in the nucleus
Give 4 facts about electrons
Charge, location, size, mass
? Negatively charged
? Move around the nucleus in electron shells
? They’re very small, but cover a lot of space
? Have virtually no mass
What are the charges and masses of the following?
a) Protons
b) Neutrons
c) Electrons
Protons: Charge = +1 Mass = 1
Neutons: Charge = 0 Mass = 1
Electrons: Charge = ?1 Mass = 0.0005
Why do neutral atoms have no charge overall?
Because they have the same number of protons as electrons
the charge on the electrons is the same size as the charge on the protons but opposite so they cancel out
What is the top number of an atom?
Eg 23
Na
11
The mass number
What does the mass number tell us?
The number of protons and neutrons
What is the bottom number of an atom?
Eg 23
Na
11
The atomic number
What does the atomic number tell us?
The number of protons
What are the verticle columns of the periodic table called?
Groups
What does the group of an element correspond to?
The number of electrons it has in its outer shell
What are the rows of the periodic table called?
Periods
What does the period to which the element belongs to correspond to?
The number of shells of electrons it has
What are isotopes?
Isotopes are different forms of the same element, which have the same number of protons but a different number of neutrons
Eg. Carbon 12 (6p,6e, 6n) and Carbon 14 (6p, 6e, 8n)
What happens in ionic bonding?
Atoms lose or gain electrons to form charge particles (ions) which are then strongly attracted to each other
What does ionic bonding occur between?
A metal and a non?metal
Explain the structure ionic compounds form
Produce giant ionic structures = the ions form a closely packed regular lattice arrangement. The ions are not free to move and so do not conduct electricity. There are very strong chemical bonds between the ions
Give two examples of giant ionic structures
- MgO = Magnesium Oxide
2. NaCl = Sodium Chloride
Why do magnesium oxide and sodium chloride have high melting and boiling points?
They have a very stong attraction between the oppositely charged ions in the structures and so to break the bonds you need lots of energy to overcome the forces of attraction
Why does magnesium oxide have a higher melting point than sodium chloride?
? It’s made of Mg(2+) and O(2?) ions which have double the charge of Na(+) and Cl(?) ions so the attraction is harder to overcome.
? Also O(2?) ions are smaller than Cl(?) ions so the ions in MgO can pack together more closely = attraction harder to overcome
What happens when metals form ions?
They lose electrons to form positive ions
What happens when non?mentals form ions?
They gain electrons to form negative ions
How do you work out the charge on the ion?
It is the same as the number of electrons lost or gained
Eg. If two electrons are gained then the charge is ?2
Eg. If three electrons are lost, the charge is +3
What is covalent bonding between?
Two non?metal atoms combine by sharing pairs of electrons
Why are the melting points and boiling points of simple molecular structures formed from covalent bonds usually very low?
Because the forces between the molecules are very week and are easily parted from each other
Why don’t molecular substances conduct electricity?
Don’t have free electrons or ions
What metals are in group 1?
Lithium, sodium, Potassium, Rubidium, Caesium and Francium
What happens to the reactivity as you go down the alkali metals?
Reactivity increases because the outer electron is more easily lost because it’s further from the nucleus so less energy is needed to remove it
Why are the alkali metals very reactive?
They all have one outer electron
What 3 physical properties do the alkali metals share?
- Low melting points and boiling point
- Low density
- Very soft
Will the alkali metals form covalent or ionic compounds?
They are keen to lose the oiter electrons to form a 1+ ion with a stable electronic structure