Chapter 2 - Atoms, Ions and Compounds Flashcards
what does an atom consist of?
- the nucleus: made up of protons and neutrons
- electrons arranged around the nucleus in shells
what are the relative masses of protons, neutrons and electrons?
proton: 1
neutron: 1
electron: negligable
what are the relative charges of protons, neutrons and electrons?
proton: +1
neutron: 0
electron: -1
where is an atoms mass?
nearly all of an atoms mass is in the nucleus
what is an atoms charge?
atoms have a charge of 0 as they have the same number of protons as electrons so the charges cancel
what is atomic number?
the number of protons in an atom. every atom of the same element contains the same number of protons.
what is an isotope?
atoms of the same element with different numbers of neutrons and therefore different masses
what is the symbol and definition of mass number?
symbol: A
definition: total number of protons + total number of neutrons
what is the symbol and definition of atomic number?
symbol: Z
definition: total number of protons
do different isotopes of an element react in the same way?
- chemical reactions involve the electrons surrounding the nucleus
- different isotopes of the same element have the same number of electrons
- the number of neutrons has no effect on reactions of an element
what is a cation?
a positive ion, an atom with less electrons than protons so has an overall positive charge
what is a anion?
a negative ion, an atom with more electrons than protons so has an overall negative charge
what is one atomic mass unit (1 u)?
1/12th of an atom of carbon-12 and approximately the mass of a proton or neutron
what is the definition of relative isotopic mass?
the mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
what can you assume relative isotopic mass is the same as?
the mass number A of the isotope
what is relative atomic mass?
the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12
what does weighted mean mass take account of?
- the percentage abundance of each isotope
- the relative isotopic mass of each isotope
how can you find the percentage abundances of the isotopes in a sample of an element?
using a mass spectrometer
how do mass spectrometers work?
- a sample is placed in the mass spectrometer
- the sample is vaporised and then ionised to form positive ions
- the ions are accelerated. heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each element are separated
- the ions are detected on a mass spectrum as a mass-to-charge ration m/z. this is roughly equivalent to the relative isotopic mass
which side of the periodic table form cations?
the left
which side of the periodic table form anions?
the right
what happens when elements can form several ions with different charges?
the ionic charge is shown with a roman numeral in the name of the ion e.g. iron (III)
what is a binary compound?
a compound that contains two elements only
how do you name a binary compound?
use the name of the first element but change the ending of the second elements name to -ide
for ionic compounds, the metal ion always comes first
what is the charge on ammonium (NH4)?
1+
what is the charge on hydroxide (OH)?
1-
what is the charge on nitrate(NO3)?
1-
what is the charge on nitrite(NO2)?
1-
what is the charge on hydrogencarbonate(HCO3)?
1-
what is the charge on manganate(VII)/permanganate(MnO4)?
1-
what is the charge on carbonate(CO3)?
2-
what is the charge on sulphate(SO4)?
2-
what is the charge on sulphite(SO3)?
2-
what is the charge on dichromate(VI)(Cr2O7)?
2-
what is the charge on phosphate(PO4)?
3-
how do you write the formula of an ionic compond?
balance the charges so the overall charge is zero
what elements are seen as molecules?
H2, N2, O2, F2, Cl2, Br2, I2, P4 and S8 (Sulphur is written as S for equations)
how are elements shown in equations?
just as their symbol (apart from elements seen as molecules)
what are the state symbols?
(g) - gas
(l) - liquid
(s) - solid
(aq) - dissolved in water (aqueous)
what are the rules of balancing equations?
- you must not change any chemical formula
- balancing numbers go in front of chemical formula and aren’t written as subscript
- the equation is balanced when there are the same number of atoms of each element on each side of the equation
what happens when you have to balance formulae with brackets?
the balancing number multiplies anything within the bracket
