1a) - Periodicity Flashcards
Explain groups
Vertical columns within the table contain elements with similar chemical properties, resulting from a common number of electrons in the outer shell
Explain periods
Rows of elements arranged with increasing atomic number, demonstrating an increasing number of outer electrons and a move from metallic to non - metallic characteristics
What is covalent radius a measure of and how can we describe the trends
Covalent radius - a measure of the size of an atom. The trends in covalent radius across periods and down groups can be explained in terms of the number of occupied shells and the nuclear charge.
What is the trend in Covalent radius going down a group
As you go down a group there is another shell or energy level of electrons so the size of the atoms increases
What is the trend in Covalent radius going across a period
As you go across a period the positive charge on the nucleus increases.
The shells or energy levels of electrons are strongly attracted to the nucleus so the size of the atoms decrease
What do atoms in the same period have the same of
Atoms in the same period have the same number of energy levels or shells of electrons
First ionisation energy
The first ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms.
M(g) —> M+ (g) + e-
Second ionisation energy
The second ionisation energy of an element is the energy required to remove a second mole of electrons
M+(g) —> m2+ (g) + e-
Third ionisation energy
The third ionisation energy of an element is the energy required to remove a third mole of electrons
M2+(g) —> M3+(g) + e-
What happens to ionisation energies across periods
Ionisation energies increase across periods because the nuclear charge increases, greater attraction for the electrons so more energy needed
What happens to ionisation energies down groups
Ionisation energies decrease down groups because more energy levels added, electrons further away from the pull of nuclear charge
Why is there a large increase from the second to the third ionisation energy
There is a large increase for magnesium from the second to third IE because the third electron is in the next shell closer to the nucleus (greater pull so therefore required more energy)
What is the screening (shielding) effect
The screening (shielding) effect is when the inner electron shells shield the nuclear pull from the outer electrons
What is electronegativity
Electronegativity is a measure of the attraction an atom involved in a bond has for the electrons of the bond
What happens to electronegativity across a period
Electronegativity increases across a period because increase in nuclear charge so greater attraction for bonding electrons
