Atomic Structure

what are atoms

the smallest particle of an element

what are elements

made of only one type of atom e.g. O₂

what are compounds

two or more elements chemically bonded together e.g. H₂O

what are mixtures

two or more substances that are not chemically bonded e.g. air

what is the rough radius of an atom

about 0.1nm (1×10^-10 m)

what is the rough radius of the nucleus

1/10,000 of that of the atom

what are the charges of the subatomic particles

• Proton: +1

• Neutron: 0

• Electron: -1

what is the mass of the subatomic particles

• Proton: 1

• Neutron: 1

• Electron: 0

what is the overall charge of an atom and why

• 0

• atoms have equal numbers of positive protons and negative electrons

Why do ions have overall charges

The number of negative electrons changes so it no longer matches the number of positive protons

where is the mass of an atom concentrated

in the nucleus

how do you calculate the number of protons from the atomic and mass numbers

number of protons is the atomic number of the element

How do you calculate the number of electrons from the atomic and mass numbers

the number of electrons is the same as the number of protons

how do you calculate the number of neutrons from the atomic and mass numbers

mass number - atomic number

what is an isotope

atoms of the same element which have the same number of protons but a different number of neutrons

what is electronic structure/electronic configuration

the arrangement of the electrons in an atom (how many electrons in each shell)

how is the modern periodic table arranged

• in order of increasing atomic number

• elements with similar properties are in groups

• metals are on the left and middle and non-metals on the right

what are the properties of metals

• shiny

• malleable

• good conductors of electricity and thermal energy

• high melting and boiling points

what are the properties of non-metals

• dull

• brittle

• poor conductors of thermal energy

• low melting and boiling points

why do elements in the same group have similar properties

they have the same number of electrons in their outer shell

what are the trends in reactivity in group 1

reactivity increases as you go down

what are the trends in reactivity in group 7

reactivity decreases as you go down

why were elements placed in the wrong group in the early periodic table

elements were arranged by atomic weight and didn’t take into account of the elements chemical properties

what is another name for group 0

the noble gases

what’s another name for group 1

alkali metals

what’s another name for group 7

halogens

why are noble gases inert

inert means unreactive. They are inert because they have a full outer shell of electrons

what is the trend in the boiling point of the noble gases as you go down the group

all the noble gases have low boiling points because as you go down the group the atoms are larger, meaning the intermolecular forces between the atoms become stronger so more energy is needed to overcome those forces

Why do alkali metals become more reactive down the group

they all have 1 electron in their outer shell. As you go down the group the atomic radius and shielding increases so there’s a weaker electrostatic attraction between the outer electron and the protons in the nucleus, so less energy is needed to lose the outer electron which makes the reaction easier to occur

why do the halogens get more reactive up the group

as you go up the group, the atomic radius and shielding decreases so there is a stronger electrostatic attraction between the outer electrons and the protons in the nucleus, so electrons are gained more easily which makes the reaction easier to occur