alkali metals
halogens
very reactive (with air) because the outer electron has a weaker attraction to the nucleus
because all halogens have 7 electrons in their outer shell
they have the same number of electrons in their outer shell
reactivity increases
atoms are always trying to gain a full outer shell and halogens have 7 so they need 1 more to be stable
unreactive because they dont need to join to other atoms/ they have a fuller outer shell
theh all have 1 electron in their outer shell, so theyll all have similiar reactions
the attraction between nucleus and outer electron gets weaker - so an electron is more easily lost. they do this to become more chemically stable.
noble gases
a substance made from one type of atom only.
tiny particles called atoms, they contain protons, neutrons and electrons
a substance made up of two or more different chemical elements
mass=sum of protons + neutrons in nucleus
neutrons= mass-protons
the opposite charges of protons and electrons cancel eachover out. making it neutral.
how many protons the atom contains
positively charged as it contains the protons.
23
Na
11
23 -> mass number
Na -> element symbol
11 -> atomic number
1st: 2
2nd: 8
3rd: 18
mass-1
charge-1
mass- -1
charge- -1
mass-1
charge-0