chemstry eoy 9
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122 Terms
what is an atom
smallest part of an element that can exist
what is Dalton’s model of the atom?
atoms as solid spheres that could not be divided into smaller parts
what is the plum pudding model of the atom?
sphere of positive charge with negative electrons embedded in it
what did scientists discover in the alpha scattering experiment?
some alpha particles were deflected by the gold foil- this showed that an atom’s mass and positive charge must be concentrated in one small space- the open nucleus
describe the nuclear model of the atom
dense nucleus with electros orbiting it
what did Neils Bohr discover
electrons obit in fixed energy level (shells)
what did Jams Chadwick discover?
uncharged particles called the neutron
where are protons and neutrons?
in the nucleus
what is the relative mass of each sub-atomic particle?
proton:1, neutron:0, electron:-1
what is the relative charge of each sub-atomic particle?
proton: +1, neutron: 0, electron: -1
how can you find out the number of protons in an atom?
the atomic number on the periodic table
how do you calculate the number of neutrons in an atom?
mass number - atomic number
why do atoms have no overall charge
equal number of positive protons and negative electrons
how many electrons would you place in the first, second and third shells
1 in the first shell up to 8 in the second and third shells
what is an element?
substance made of one type of atom
what is a substance
substance made of more than one type of atom chemically joined together
what is a mixture
two or more substance not chemically combined
what are isotopes?
atoms of the same element (same number of protons with different numbers of neutrons)
what are the four physical processes that can be used to separate mixtures
filtration, crystallisation, distillation, fractional distillation, chromatography
what is relative mass
the average mass of all the atoms of an element
what is an ion
atom that has lost or gained electrons
what kinds of elements form ionic bonds
metals and non-metals
what charges do ions from group 1 and 2 form?
group 1 forms 1+
group 2 forms 2+
what charges do ion form groups 6 and 7 form
group 6 forms 2-, group 7 forms 1-
name the force that holds oppositely charged ions together
electrostatic force of attraction
why don’t ionic substances have high melting points?
electrostatic force of attraction between positive and negative ions held together by electrostatic force of attraction
describe the structure of a giant ionic lattice
regular structure of alternating positive and negative ions held together by the electrostatic force of attraction
why do ionic substance conduct electricity when melted or dissolved
ions are free to move and carry charge
how is modern periodic table?
by atomic number
how were the early lists of elements ordered?
by atomic mass
why did Mendeleev leave gaps in his periodic table?
leave room for elements that had not yet been discovered
why did Mendeleev leave gaps in his periodic table?
leave room for elements that had not yet been discovered
why do elements in a group have similar chemical properties
because they have the same number of electrons in their outer shells
where are metals and non-metals located on the periodic table?
metals to the left, non-metals to the right
what name is given to the Group 1 elements?
alkali metals
what is the general equation for reactions of alkali metals with oxygen
metal + oxygen —→ metal oxide
what is the general equation for the reactions of alkali metals with chlorine
metals + chlorine —→ metal chloride
what is the general equation for the reactions of alkali with water
metal + water —→ metal hydroxide + hydrogen
how does the reactivity of alkali metals increase down the group?
more reactive as you go down the group
why does reactivity of alkali metals increase down the group?
they are larger atoms, so the outermost electron is further from the nucleus, meaning there are weaker electrostatic forces of attraction and more shielding between the nucleus and out electron and it is easier to lose the electron
what name is given to the group 7 elements
halogens
give the formulae of the first four halogens
F2, Cl2, Br2, I2
how do the melting points of halogens change down the group
increase as you go down the group
how does the reactivity of the halogens change down the group
the reactivity decreases going down the group
why does the reactivity of the halogens change down the group
they are larger atoms, so the outermost shell is further from the nucleus meaning there are weaker electrostatic forces of attraction and more shielding between the nucleus and outer shell and it is harder to gain an electron
what is a displacement reaction?
when a more reactive element takes the place of a less reactive one in a compound
what is the name given to the Group 0 elements
noble gases
why are the noble gases inert?
they have full outer shells so do not need to lose or gain electrons
how do the melting points of the noble gases change down the group
the melting point increases down the group
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