Chapter 7 Flashcards
What do groups in the periodic table show? How does this relate to the elements?
- Groups in the periodic table have the same number of electrons in their outer shell, and similar chemical properties
What is periodicity? Required.
- Repeating trends in the physical and chemical properties of elements across a period
What are 4 properties that have periodicity?
- Electronic configuration
- Ionisation energy
- Structure
- Melting points
What trend do periods have in terms of electronic configuration?
- Each period starts with an electron in the new highest energy level
What is first ionisation energy? Required.
- The energy required for the removal of 1 mol of electrons from 1 mol of gaseous atoms of an element
Write an equation for the first ionisation energy of chlorine.
- Cl (g) -> Cl+(g) +e- (it is not shown as diatomic as first ionisation energy refers to 1 mol of atoms)
What is second ionisation energy?
- The amount of energy needed to turn 1 mol of gaseous 1+ ions into 1 mol of gaseous 2+ ions
What 3 factors affect ionisation energy?
- Atomic radius
- Nuclear charge
- Electron shielding
How does atomic radius affect ionisation energy?
- The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction
How does nuclear charge affect ionisation energy?
- The more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons
How does electron shielding affect ionisation energy?
- Electrons are all negatively-charged and therefore repel each other, meaning that inner-shell electrons repel outer-shell electrons
- This reduces the attraction between the nucleus and the outer electrons
How do successive ionisation energies compare with each other?
- They increase
- There is a big increase in the ionisation energy between different shells of an atom
Why do successive ionisation energies increase?
- The atomic radius decreases
- The nuclear attraction between the remaining electrons and nucleus increases (the same number of protons attract fewer electrons)
Describe the trends in first ionisation energy in the periodic table.
- They decrease down a group (down across the different periods)
- They generally increase across a period
Why does first ionisation energy decrease down a group?
- The atomic radius and shielding increases
- Nuclear attraction on outer electrons decreases