Key Terms In Chemistry Flashcards
(89 cards)
JJ Thompson’s Plum Pudding Theory
Positively charged sphere
With electrons that are negatively charged atoms
Rutherfords Model
Tiny positively charged nucleus at the centre
Surrounded by a cloud of negative electrons
Most of the atom is empty space
Gold Leaf Test - Rutherford
Fired positively charged alpha particles at a thin gold sheet.
Most particles went straight through, some were deflected and a small number were backwards- so the plum pudding could not be right
Bohr’s Model
Electrons only exist in fixed orbits or shells
Each shell has a fixed energy
Protons
- relative mass
- relative charge
Heavy and positively charged
Relative Mass - 1
Relative Charge - +1
Found in the nucleus which is positively charged
Neutrons
Heavy Neutral Relative mass - 1 Relative charge - 0 Found in nucleus
Electrons
Negative
Relative mass- 0.0005
Relative Charge - -1
Found in electron shells
Atomic number
Tells you how many protons and electrons there are in the atom
Mass number
Tells you the total number of protons and neutrons in an atom
Isotopes
Different forms of the same element, which have the same number of protons but a different number of neutrons.
How do you calculate the relative atomic mass from isotopic abundances?
Multiply each relative atomic mass by its isotopic abundance and add up the results
Divide by the sum of the abundance’s
How did the order of the periodic table come about?
Dmitri Mendeleev arranged them based on their properties, then realised they were in order of atomic mass
What do periods show in the periodic table?
Represent a new full shell of electrons
What do groups show on the periodic table?
Corresponds to the number of electrons it has on its outer shell
Ions
Ions are charged particles- when atoms lose or gain electrons to form ions
When do negative atoms form?
Anions - when atoms gain electrons- they have more electrons than protons so they are negatively charged
When do positive ions form?
Cations- when atoms lose electrons - they have more protons than electrons - they are positively charged
Group 1 and 2 ions
They are metals so they lose electrons to form positive ions
Group 6 and 7 ions
Non metals that gain electrons to form negative ions
Ionic bonding
When a metal and non metal react together
- the metal atoms loses electrons to form a positive ion
- the non metal gains these to form a negative ion
What are oppositely charged ions attracted to each other by?
They are strongly attracted to one another by electrostatic forces this is called an ionic bond
Ionic compound shapes
Always have a giant ionic lattice structures. The ions form a closely packed regular lattice
There are very strong electrostatic forces of attraction between oppositely charged ions in all directions
Ionic compound properties
-melting and boiling points
High melting and boiling points due to the strong attraction between the ions. It takes a large amount of energy to overcome this attraction.
Ionic compound properties
-conductor of electricity?
Solid ionic compounds don’t conduct electricity because the ions are in a fixed place and can’t move.
But when an ionic compound melts, the ions are free to move and can carry an electric current.