M3 Chapter 7 - Periodicity Flashcards
How is the periodic table arranged?
By chemical and physical properties and Atomic Number.
What does atomic number have to do in the periodic table?
From left to right the elements are arranged in order of increasing atomic number. Each successive element has atoms with one extra proton.
What is a group?
Elements are arranged into vertical columns called groups. Each element in a group has atoms with the same number of outer-shell electrons and similar properties.
What is a period?
The elements are arranged into horizontal rows called periods. The number of the period gives the number of the highest energy electron shell in an element’s atoms.
What is periodicity?
The repeating trend in properties across the periodic table.
What topics/properties influence periodicity?
Electron configuration, ionisation energy, structure and melting point.
What is the trend in electron configuration across a period?
Each period starts with an electron in a new highest energy shell: Across period 2 the 2s subshell fills with 2 electrons follwed by the 2p subshell with 6 electrons. Across period 3 it is the same as period 2.
What is the trend in electron configuration down a group?
Elements in each group have atoms with the same number of electrons in each subshell. This similarity in electron configuration gives elements their similar chemistry.
What are the four blocks of the periodic table?
S, P, D, F
What is ionisation energy?
Ionisation energy measures how easily an atom loses electrons to form positive ions.
What is the definition of first ionisation energy?
The first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.
Give an example of a first ionisation energy equation…
Na(g) –> Na+(g) + e-
What factors affect first ionisation energy?
Atomic Radius, Nuclear Charge, Electron Shielding
What is the effect of Atomic Radius on the ionisation energy?
The greater the distance between the nucleus and the outer electrons the less the nuclear attraction. Hence ionisation energy is lower if there is an increase on atomic radius.
What is the effect of Nuclear Charge on the ionisation energy?
The more protons there are in a nucleus of an atom, the greater the attraction between the nucleus and the outer electrons. Hence ionisation energy is higher if there is an increase of nuclear charge.
What is the effect of Electron Shielding on ionisation energy?
Electrons are negatively charged hence, inner shell electrons repel outer shell electrons. This repulsion is called the shielding effect. Hence an increase of electron shielding, the lower the attraction between the nucleus and the outer electrons hence ionisation energy is lower.
Give an example of a successive ionisation energy equation.
He(g) –> He+(g) + e- First Ionisation Energy
He+(g) –> He2+(g) + e- Second Ionisation Energy
What is the definition of second ionisation energy?
The energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions.
What do successive ionisation energies show us for different energy levels in an atom?
In the successive ionisation energies of Fluorine, the large increase between the seventh and eighth electron shows that the eighth electron must be removed from a different shell, closer to the nucleus and with less shielding.
What predictions can we make from successive ionisation energies?
- The number of electrons in the outer shell
- The group of the element in the periodic table
- The identity of an element.
What is the trend in ionisation energy down a group?
The first ionisation energies decrease down a group.W
Why does ionisation energy decrease down the group?
The atomic radius increases.
There are more inner shells therefore electron shielding increases.
The nuclear attraction on outer electrons decreases.
Therefore, the overall first ionisation energy decreases because less energy is required to remove the electron.
What is the trend in first ionisation energy across a period?
There is a general increase in first ionisation energy across a period.
Why is there a general increase across the period in first ionisation energy?
Nuclear charge increases.
Same shell therefore shielding remains the same.
The nuclear attraction increases due to the nuclear charge increasing.
The atomic radius decreases too due to this.
The first ionisation energy increases.