Unit 2: Periodic Table trends Flashcards
(50 cards)
Whats the trend in effective nuclear charge?
Increases across a period but remains approximately the same down a group
Explain the trend in atomic radius.
Atomic radius increases down a group (the number of occupied electrons levels increases) and decreases across a period
Explain the trend in Ionic radius.
- Increases down a group(# of electron energy levels increase)
- decreases across a period (because of the increased attraction between the nucleus and outer electrons)
Why are negative ions larger then their parent atoms?
The addition of electrons to the outer energy level increases the electron repulsion from the the electrons in the outer principle level causes the electrons to move further apart and therefore the radius increases.
Explain the trend in ionization energy.
- Increases across a period ( the increase in effective nuclear charge increases the attraction between the outer electrons and the nucleus making the electrons difficult to remove)
- Decreases down a group ( the electron removed is from the energy level furthest from the nucleus, the effective nuclear charge is about the same b/c of the shielding from the inner electrons.
Define electron affinity.
The energy change that occurs when one mole of electrons is added to one mole of gaseous atoms.
Explain the trend in electronegativity.
- Decreases down a group The bonding electrons are furthest from the nucleus and the little shielding) and increases across a period (because of the increase in in nuclear charge resulting in an increased attraction between the nucleus and the bond electrons.
Explain the trend in electron affinity
- Decreases down a group
- Increases across a period
Explain electronegativity.
The ability of an atom to attract electrons in a covalent bond
What are chemical properties determined by?
The electron configuration of its atoms
- Elements of the same group have similar chemical properties as they have the same number of valence electrons in their valence orbitals.
Describe the properties of group 1 elements (alkali metals)
Physical
- good conductors of electricity and heat
- They have low density’s
- Shiny grey surfaces when freshly cut with a knife
Chemical
- Reactive
- Form ionic compounds with non-metals
Describe the properties of group 17 elements (Halogens)
Physical
- They are coloured
- They show a gradual change from gases (F2 and Cl2), to liquid (Br2), and solids (I2 and At2)
Chemical
- Very reactive non-metals
- Reactivity decreases down the group
- They form ionic compounds with metals and covalent compounds with other non-metals
The oxides of P, S, Cl have what structure?
Molecular covalent
The oxides of elements Na to Al have what structure?
Giant Ionic
The oxide of silicon has what structure?
Giant covalent.
What is the trend in oxides?
They become more Ionic down a group as the electronegativity decreases.
When do oxides conduct electricity?
When in the liquid or aqueous state when the ions are free to move.
What structures are associated with high melting points?
Ionic
What structure is associated with low melting points?
Molecular covalent.
Metallic elements form what oxide and are acidic or basic?
Ionic oxides and basic
Non-metals form what oxide and are acidic or basic?
Covalent and acidic
Aluminium oxide shows what properties
Amphoteric ( reacts with both acids and bases)
Alkalis are bases that are soluble in water. What do they for, in an aqueous solution?
They form hydroxide ions.
Why is rainwater naturally acidic?
Due to disolved CO2 pH<5.6
