Unit 3. Periodic Table Flashcards
What is the nuclear charge
The number of protons in the nucleus of an atom. Basically the atomic number
Name of vertical columns and horizontal row
Group and period
What does the period number tell you?
The number of occupied main energy levels in an atom
What does the group number tell you?
The number of valence electrons in an atom of that element
Where are metals, non-metals and metalloids located on the periodic table?
Metals located mainly on the left and middle in the s-, f- and d-block.
Non-metal elements are found on the right side in the p-block.
Metalloids (semi-metals) are located in a diagonal staircase that forms a boundary between metals and non metals.
Name the name of the groups in the periodic table and where they are found, as well as their characteristic properties
Alkali Metals- Group 1- most reactive, react strongly with water
Alkaline earth metals- Group 2- reactive but less reactive then group 1
Halogens- Group 17- most reactive group of non-metals
Noble gases- Group 18- very unreactive monatomic gases
Transition metals- D-Block region (apart from zinc)- relatively stable with only moderate reactivity useful for construction
What are the lanthanides and actinides
They are metallic elements that make up the f-block. Their two rows are separated from the rest of the periodic table. Atomic numbers from 89-103, they are radioactive. Lanthanides (57-71) are knows as rare earth metals
What are the s- p- d- and f- block directly correlated to?
The electron configuration with the sub levels: s,p,d,f. The block in which an element is tell us which sub-level is in the process of being filled.
How do you find the v.e of group 13 to 18?
Substract ten from group number.
What is atomic radii
The size of an atom
Trend in atomic radii?
Period
Starting with sodium (11) it decreases across the period until it reaches chlorine (17). Bc we gain an electron and a proton as we go across a period, electron shielding remains more or less constant, as the electrons fill the same main energy level. Therefore there is an increased attraction between the nucleus and outer electrons which pulls them closer.
Group
Going down a group, each element’s v.e occupies another extra main energy level which increases the atomic radii.
What is electron shielding?
Electron shielding occurs when outer electrons are shielded from the attraction of the nucleus by inner electrons knows as shielding electrons.
Which are more likely to become anions and cations, metals or non metals?
Metallic elements tend to loose electrons and form cations.
Non metallic elements tend to gain electrons and form anions
What are isoelectronic species?
Isoelectronic species have the same electron configuration. Example: Na+, Mg2+. They have different numbers of proton but same of electrons.
What is the ionic radius
The distance between the nucleus of an ion and the outermost energy shell of the ion
When does the ionic radius increase?
When the number of proton decrease
More positively charged cations have the smallest ionic radius, and more negatively charged anions have the largest radius.
Explain ionic radius trend in period 3
- first 4 cations have lost their outer energy levels of elections and now occupy one less energy level. Since the nucleus is pulling on fewer electrons, the attraction increases between the nucleus and the v.e, which reduces the ionic radius.
- anions are bigger than their parent atom as they gain electrons which reduces the attraction by the nucleus. The extra electrons also increase repulsion between electrons. This all makes the ionic radii increase.
- across a period the ionic radii decreases as the nuclear charge increases (protons higher)
What is effective nuclear charge
The attraction felt by v.e which are further away from the nucleus and are shielded by other electrons.
How do you calculate the effective nuclear charge?
Take sodium (11). The 11th electron in the last 3s sub-level is shielded by the other 10 electrons, which are closer to the nucleus, from the 11 protons. Therefore do 11 protons minus 10 electrons. That v.e effective nuclear charge is 1+.
Nuclear charge trend
Period
- across increases as proton number increases but electron number in inner energy levels remains the same. It increases by one.
Group
- remains constant , as the attraction from the increasing numbers of protons in the nucleus is offset by the increase in occupied energy levels down the group.
What is first Ionisation energy?
Ionisation Energy is the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
(A measure of the attraction between the positively charged nucleus and the negatively charged valence elections.)
General trend for first Ionisation energy
Increase across period bc of increase in nuclear charge and decrease in atomic radii, which results in an increased attraction between the nucleus and the v.e
Decrease down a group is bc of the increase in atomic radius which causes weaker attraction between the nucleus and v.e of an atom.
Exceptions to first ionization energy
Decrease in ionization energy from beryllium to boron, magnesium to aluminum, nitrogen to oxygen and phosphorus to sulfur.
Beryllium has the electron configuration 1s2 2s2
Boron has the electron configuration 1s2 2s2 2p1
Electrons in p orbitals are of higher energy and further from the nucleus than electrons in s orbitals, therefore they require less energy to remove. The same explanation can be applied for the drop in ionisation energy from magnesium to aluminium
Nitrogen has the electron configuration 1s2 2s2 2p3
Oxygen has the electron configuration 1s2 2s2 2p4
In oxygen, the electron is removed from a doubly occupied p-orbital. An electron in a doubly occupied orbital is repelled by the other electron and requires less energy to remove than an electron in a half-filled orbital. The same explanation applies for the decrease in ionisation energy from phosphorus to sulfur, except that the elect
What is electronegativity?
Electronegativity is the attraction of an atom for a bonding pair of electrons.