atomic structure and the periodic table Flashcards
what is a pure substance
consists of only one element or compound
who published the first ideas about atoms in 1803
John Dalton, tiny spheres that couldn’t be divided
who discovered the electron
JJ Thompson, led him to suggesting the plum pudding model of the atom, ball of positive charge with negative electrons embedded
who did the gold foil experiment in 1909
Ernest Rutherford
what conclusions did he make from the gold foil experiment
most passing straight through - mostly empty space
change direction - positive centre
reflecting - mass of atom concentrated in centre
who proved that electrons orbited in shells
Niels Bohr
who discovered neutrons in 1932
James Chadwick
what proportion of a nucleus is the atom
1/10.000
do isotopes of the same element have identical chemical properties
yes
when did mendeleev publish his first periodic table
1869
how did mendeleev arrange the first periodic table
- in order of increasing weight taking into account properties of elements and compounds
- this meant his table had gaps
- elements with similar properties lined up in groups
what happened as a result of mendeleev leaving gaps
he predicted properties of future elements that turned out to be true
what is an explanation for mendeleev pair resversals
different isotopes of elements existed, elements with higher relative atomic mass had lower atomic numbers
do metals lose or gain electrons
lose electrons
what is the difference between metal and non-metal oxides
metal oxides are basic
non-metal oxides are acidic
what does malleable mean
means it can be hammered into shape without breaking
what does ductile mean
means it can be made into a wire
what is group 0
noble gases - on the far right of the periodic table
why do noble gases increase in boiling points
- atoms become larger
- intermolecular forces between atoms are stronger
- more energy needed to overcome these forces
what does inert mean for noble gases
extremely unreactive
why are noble gases unreactive
they already have a full outer shell so don’t need to lose gain or share electrons
what is group 1
alkali metals - on the far left of the periodic table
physical properties of alkali metals
- soft
- low melting points
- low densities
what happens to melting points for alkali metals
decrease
what happens when alkali metals react with water
produce a metal hydroxide + hydrogen
what do alkali metals melt to form in water
a ball
what happens when alkali metals react with oxygen
produce metal oxides as white smoke
what happens when alkali metals react with chlorine
form white solid chlorides that dissolve in water to form colourless solution
why do alkali metals get more reactive
- atoms become larger
- outer electron further from nucleus
- force of attraction between nucleus and outer electron decreases
- outer electron lost more easily
what is group 7
halogens on the second to right hand side of periodic table
how do halogens exist
a pair of halogen atoms joined by a single covalent bond
what happens to melting and boiling points in halogens
increase as you go down because
- molecules become larger
- intermolecular forces become stronger
- more energy needed to overcome these forces
what happens when a halogen reacts with metals
produces salts held together by ionic bonds
what happens to reactivity as you go down halogens
decreases
what happens when a halogen reacts with hydrogen
hydrogen halide is formed gas at room temperature which dissolve in water to produce acidic solutions
reactivity series
potassium sodium calcium magnesium aluminium carbon zinc iron tin lead hydrogen copper silver gold platinum
properties unique to transition metals
- higher melting points
- higher densities
- greater strength
- greater hardness
what coloured compounds do the different metals form
not transition - white compounds
transition - coloured compounds
what is a catalyst
substance that increases rate of reaction without being used up
