Topic 1 - Atomic Structure and Periodic Table Flashcards
Charge of a proton
+1
Charge of a neutron
0
Charge of an electron
-1
where are the electrons
in electron shells around the nucleus
why do atoms have no overall charge
same number of protons and electrons
ions have an overall charge, why?
number of protons and electrons aren’t equal
what is atomic number?
how many protons there are
what is mass number?
total number of protons and neutrons in an atom
if a substance only contains atoms with the same number of protons what is it
an element
what are isotopes
different forms of the same element, same number of protons but a different number of neutrons
how are compounds formed
elements react, atoms combine
what are compounds
substances formed from two or more elements, held together by chemical bonds
what needs to happen for bonds to be made
atoms need to give away, take or share electrons
how can you separate out the original compound
a chemical reaction
what happens in ionic bonding?
a metal and non metal combine, the metal atom loses electrons to form positive ions, the non metal atom gains electrons to form a negative ion
they also have opposite charges, meaning they are strongly attracted to each other
what happens in covalent bonding?
non metals combine, each atom hares an electron with another atom
how are compounds represented
formulas
bonding in a mixture
there are no chemical bonds between the different parts of a mixture, so are easily separated
what methods can be used to separate a mixture
filtration crystallisation simple distillation fractional distillation chromatography
examples of a mixture
air - mixture of gases
crude oil - mixture of different length hydrocarbon molecules
What did J J Thomson conclude
Atoms weren’t solid spheres, contain electrons
What did the plum pudding mode show
The atom as a ball of positive charge with electrons stuck randomly in it
How did Rutherford show that the plum pudding model was wrong
The alpha particle scattering experiment, fired positively charged alpha particles at a sheet of thin gold
Most particles went straight through (empty space)
And a small number were deflected
What was Bohr’s model
The nuclear model, a positively charged nucleus, surrounded by a cloud of negative charge (Rutherford) then Bohr discovered electrons were contained in shells and orbit the nucleus
Electron shell rules
Electrons always occupy shells
Lowest energy levels are filled first
2,8,8…
All atoms want to be stable and have a full outer shell (like noble gases)
How was the periodic table originally arranged
Atomic mass
How did Mendeleev organise the periodic table
Order of atomic mass, and groups of elements with similar properties
Why were their gaps left in the periodic table
Space for undiscovered elements
