U3.1: Periodicity Flashcards
Properties of metals
- act as conductor of heat and electricity
- forms cations by losing electrons
- typically lustrous
- Most of the elements are metals
Properties of non-metals
- Doesn’t act as a conductor of anything
- Forms anions by gaining electrons
- Typically dull in solid state but most are non-metals
Property of metalloids
- Semi metal
Properties of groups
- Elements in same group have similar chemical properties and show a trend in physical properties
- This is because they have the same number of valence electrons
Properties of periods
- Elements in the same period have the same number of electron shells
- This is because the number of electron shells affect the size of the element
List the metalloids
B, Si, Ge, As, Sb, Te, Po
Define effective nuclear charge
Net positive charge from the nucleus experienced by outer valence shell electrons once the screening effect of the core electrons has been considered
Define Periodicity
Refers to repeating trends or patterns of physical & chemical properties in elements
Define atomic radius
Distance from an atom’s nucleus to the outermost orbital of 1 of its electrons
Define isoelectric
Molecules that have the same electronic configuration
What is the trend in the atomic radius
Across a period:
- decreases as electrons are added to the same main energy level (n = 3)
- effective nuclear charge increases
- attraction between nucleus and valence electrons increases
Down a group:
- increases as number of electron shells increases
What is the trend in the ionic radius
POSITIVE IONS:
Across a period:
- decreases as the number of valence electrons decreases
- attraction between nucleus and valence electrons increases
- greater the number of electrons removed, the smaller the ionic radius
NEGATIVE IONS:
Across a period:
- increases as number of valence electrons increases
- attraction betwee the nucleus and valence electrons decreases
- greater the number of electrons gained, the larger the ionic radius
Define Ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
Define first ionisation energy
Energy required to remove one mole of the most loosely held electron from one mole of neutral gaseous atoms to form one mole of gaseous 1+ ions
What is the trend in ionisation energy
Across a period:
- increases as the number of protons increases in the nucleus and there are more electrons occupying the outer valence shell
- there’s an increase in effective nuclear charge
- there’s a greater number of electrons in the outer valence shell hence, there’s a stronger attraction to the nucleus
- More energy is required to remove an electron
Down a group:
- decreases as the atomic radius increases and electrons occupy higher energy levels
- Electrons in higher energy levels have a weaker attraction to the nucleus-
- Less energy is required to remove an electron
Define Electron Affinity
The amount of energy released when a neutral atom gains an electron to form an anion
What is the trend in electron affinity
Across a period:
- increases as there is an increasing effective nuclear charge
- stronger attraction between added electrons and nucleus
Down a group:
- decreases as elements further down have a larger atomic radius, with outer valence shells further away from the nucleus
- weaker attraction between the added electrons and nucleus
What are the excepts to the trend of electron affinity
- F and Cl
- Since they’re so small, it’s hard to add more electrons to its much higher electron density
How high is the electron affinity in metals and non metals
- Metals have a low EA
- Non-metals have a high EA
Define electronegativity
the tendency of an atom to attract electrons in a chemical bond
What is the trend in electronegativity
Across a period:
- increases as effective nuclear charge increases
- stronger attraction between nucleus of atom and shared pair of electrons
Down a group:
- decreases as atomic radius increases from additional energy levels
- Weaker attraction between nucleus of an atom and shared pair of electrons
How high is the electronegativity in metals and non-metals, why?
- metals have low EN as they lose electrons easily
- non-metals have high EN as they gain electrons to complete their outer valence shell
What is one exception to conducting electricity whilst being a non-metal
Graphite
Define metallic character
Tendency of an element to lose electrons to form cations
Define non-metallic character
Tendency of an element to gain electrons to form anions
Trend in metallic character?
From bottom left to top right of periodic table, MC increases
Trend in non-metallic character?
From bottom left to top right of periodic table,
NMC increases
All Chemical trends of Group 1 (Alkali Metals) Down the group
- Atomic/ionic radius increases: Increasing e- shells
- EN and1st IE decreases: Increased distance between V. e- and nucleus hence, easier to remove
- MP decreases: Atomic radius increases hence, metallic bonds become weaker
- Reactivity increases: V. e’s easier to lose due to greater shielding of inner e-