Atoms and elements Flashcards
what is an element
made up of only one type of atom
what is a compound
two or more different types of elements chemicaly bonded in fixed proportions.
what is a mixture
two or more diffrent elements not chemically combined
what are sub atomic particles of an atom
proton, neutron and electron
what does the nucleus of an atom contain
proton and neuton
what is the mass of proton, neutron and electron
neutron = 1
proton = 1
electron = 0.0005 or very small
what is the charge of proton, neutron and electron
proton = +1
neutron = 0
electron = -1
location of electron
orbit shells
what does the atomic number tell you about an atom
no of protons
what does the mass number tell you about the atom
protons + neutrons
neutrons =
mass number - atomic number
why are atoms uncharged particles
they have the same number of protons and electrons that opposite charges, so they camcel each other out.
what are isotopes
atoms of the same element with the same number of protons but different number of neutrons
what is relative atomic mass
average mass of an element, taking into account the differnt masses of the isotopes, along with their relative abundances
formula for relative atomic mass
sum of ( isotope abundance * isotope mass number)/ sum of abundances of all the isotopes which is 100
what happens to alkali metals as they go down the group
they get more reactive down the group
do alkali metals have low or high melting and boiling point
low
what happens to halogens/ group 7 as they go down the group
less reactive
some features/ properties of alkali metals
soft, shiny when cut, tarnished after shiny surface exposed
why do group 1 metals act the same way
same number of electrons on outer shell
what is reactivity
greater the tendency to lose or gain electrons
what are the factors that determine how reactive elements in a groupa are
atomic radius of an element
electron shielding
why are elements in group 1 more reactive as they go down the group
they have a larger atomic radius which means the positive nucleus is further away from the negative outer electron, so there is a weaker electrostatic force of attraction, electrons are easily lost making it more reactive.
greater electron shielding, more inner electrons to shield the positive nucleus, so a weaker electrostatic attraction between the postive nucleus and the negative outer electron, so electrons are easily lost, making it more reactive.
why is fluorine more reactive than bromine
flourine has a smaller atomic radius than bromine which means there is a stronger electrostatic attraction between the positive nucleus and the negative outer electron , making it easier to gain electrons making it more reactive than bromine.
Bromine has a greater electron shielding, so ther is weaker electrostatic attraction between positive nucleus and negative outer electron, making it harder to gain electrons, making it less reactive than bromine.