Atomic structure Flashcards
give the relative mass and charge of proton, neutron and electron
P - 1 (M) 1+ (C)
N- 1,0
E- 1/1840 , 1-
Atomic number
The atomic number (i.e. proton number), Z is equal to the number of protons.
MASS NUMBER
The mass number, A is equal to the number of protons and neutrons combined.
Positive Ions (cations)
An atom has lost electrons so that there are more protons than electrons p > e-
Negative Ions (anions)
An atom has gained electrons so that there are more electrons than protons p < e-
Isotopes
Isotopes are atoms with the same number of protons but a different number of neutrons.
In Rutherford’s model what did P find?
Rutherford fired He2+ ions at a sheet of gold foil. When the He2+ ions arrived at point P he concluded that most of the atom as empty space.
In Rutherford’s model what did Q find?
A very small number of the He2+ ions where detected at point Q He concluded that the atom must have a small positive nucleus.
The bohr model has…
A small positive nucleus The electrons surround the nucleus in energy shells (We now know that the nucleus also contains neutrons)
Ionisation energy
Ionisation energy is the amount of energy needed to remove a mole of electrons from a mole of atoms, in the gaseous state. The can be abbreviated to ‘IE’ and the units are kJmol-1
Write an equation for the 1st ionisation energy of Potassium
K(g) à K+(g) + e-
Three key factors that will influence Ionisation Energy
- Nuclear charge - More protons Stronger attraction to nucleus More energy to remove outermost electron
2.Shielding - Electron on shell further from the nucleus More shielding Weaker attraction Less energy to remove outermost electron
3.Distance from nucleus - Electron closer to nucleus Stronger attraction to nucleus More energy to remove outermost electron
Why is the second ionisation energy of B higher than the first?
The second electron is removed from an ion that already has a positive charge.
