C2 - Chemical Patterns Flashcards
History of atom
Dalton: atoms are solid spheres
JJ: Electrons, plum pudding model
Rutherford: positively charged alpha particles at thin gold; nuclear model
Bohr model: electrons orbit the nucleus in fixed shells
Group 1 elements are Reactive
alkali metals, as u go down the group: more reactive, lower melting / boiling points
What is the relative mass of protons, neutrons, and electrons?
proton = 1
neutron = 1
electron = neglible
what is the relative charge of a proton, neutron, and electron?
+1, 0, -1
what is the mass number?
the total number of protons and neutrons
what is the atomic number?
the number of protons
how did Mendeleev know how to leave gaps?
he recognised patterns in the properties of known elements and realised there must be undiscovered elements that would fit into those gaps
why is it difficult for non-metals to form positive ions?
they either have a lot of electrons to remove to get a full outer shell, or towards the top, where the outer electrons are close to the nucleus
state 3 properties of metals?
shiny appearance
tend to have high densities
great at conducting heat and electricity
state 3 properties of non-metals
dull looking
often have a lower density
poor conductors of heat and electricity
what are group 1 metals?
alkali metals
soft and have low density
what are the trends for alkali metals as you go down the group? (4)
increasing reactivity
lower melting/boiling points
higher density
higher relative atomic mass
why does the melting and boiling points decrease as you go down group 1?
as you go down, the atoms get bigger, the nucleus is further away from the free electrons; the attractions get weaker
this means less energy is needed to break the metallic bonds
why does the reactivity increase as you go down group 1?
negatively charged outer electron is less strongly attracted to the positively charged nucleus
true or false: when alkali metals are put in water, they produce nothing
false, they produce hydrogen and [alkali metal name + hydroxide]
What are group 7 elements?
halogens
7 electrons in outer shell
exist as diatomic molecules
what happens when you go down group 7? and why does this happen?
the melting and boiling points increase
as the number of electrons decrease as you go down. more electrons means there is greater intermolecular forces between molecules, so more energy is needed to overcome them
why are halogens less reactive as you go down the group?
as it gets harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus
what do halogens react with to form salts?
halogens will react vigorously with alkali metals to form salts called “metal halides”.
what is the balanced symbol equation of sodium Na and chlorine (I2)?
2 Na ( s ) Sodium + Cl 2 ( g ) Chlorine → 2 NaCl ( s ) Sodium Chloride
true or false: a more reactive halogen will displace a less reactive one
true
how can we show the trend of reactivity in group 7?
you can use displacement reactions
if there is a significant colour change, a reaction has happened
if no reaction happens, there won’t be a colour change
what are the group 0 elements?
noble gases
full outer shell apart from helium, making them energetically stable, so they’re inert
colourless at room temeprature
why does the boiling and melting points increase as you go down the group of group 0?
is due to the increase in the number of electrons in each atom, leading to greater forces between the atom to be overcome
what are negative ions?
anions
form when atoms gain electrons
what are positive ions?
cations
form when atoms lose electrons
why do ionic compounds have high melting and boiling points?
due to the strong attraction between ions
it takes a lot of energy to overcome attraction compared to other types of bonding
why don’t solid ionic compounds conduct electricity?
as the ions are fixed in a place and can’t move. but when ionic compound melts, the ions are free to move and will carry an electric charge
what are ionic compounds?
made up by positive and negative ionic held together by ionic bonds
true or false: the overall charge of an ionic compound is zero
true!!!
