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What is a compound?
Two or more different elements that are chemically combined
What is an atom?
The smallest part of an element that can exist
What is a mixture?
Two or more different elements or compounds not chemically combined
What does filtration separate?
Insoluble solids and a liquid
What does crystallisation separate?
Soluble solids from a solution
What does simple distillation separate?
Solvents from a solution
What does fractional distillation separate?
Two liquids with similar boiling points
What is paper chromatography used for?
Identifying substances from a mixture in a solution
What were atoms thought to be before the discovery of the electron?
Tiny spheres that couldn’t be divided
What did JJ Thomson discover?
The electron which promoted the development of the plum pudding model
What did Rutherford’s alpha particle scattering experiment conclude?
The mass of the atom is concentrated in the centre and this mass is positively charged
How did Niels Bohr adapt the nuclear model?
By suggesting that electrons orbit the nucleus at specific set distances
What did James Chadwick discover?
The neutron
How long after the nucleus was a widely accepted scientific idea was the neutron discovered?
20
What is the charge of a proton?
+1
What is the charge of a neutron?
0
What is the charge of an electron?
-1
What is the radius of the atom?
1×10(-10)m or 0.1 nm
What fraction of the radius of the atom is the nucleus?
1/10000
What is the relative mass of protons and neutrons?
1
What is the realtive mass of an electron?
0 (very small)
What is an isotope?
Atoms of the same element with a different number of neutrons
What is the relative atomic mass of an element?
The average value that takes into account the abundance of the isotopes of an element
How are elements arranged in the periodic table?
By atomic number
What do elements in the same group have in common?
The same number of electrons in their outer shell
How did old periodic tables arrange the elements?
By atomic weight
What was wrong with early periodic tables?
They were incomplete, and some elements were placed in inappropriate groups
How did Mendeleev overcome problems with the periodic table?
He left gaps for elements that hadn’t been discovered and changed the order based on atomic weight in some places.
Which elements form positive ions?
Metals
Which elements form negative ions?
Non-metals
What are elements in group 0 also known as?
Noble gases
How does the boiling point change as you go down group 0?
Increases
What are group 1 elements also known as?
Alkali metals
How does reactivity change as you go down group 1?
It increases
How does reactivity change as you go down group 7?
It decreases
What are group 7 elements also known as?
Halogens
