Periodicity Flashcards
What does the group number indicate
The number of valency electrons
What does the period number indicate
The number of electron shells
What group is alkali metals
group 1
What group is halogens
group 17
Define periodicity
The repeating pattern of physical and chemical properties shown by the different periods
Define Atomic radius
The distance between the nucleus and most outer electron
How is atomic radius calculated
As the position of the outer most electron is impossible to be known precisely it is taken as half the distance between the nuclei of two bonded atoms of the same element
How does atomic radius change across a group and period and why
Atomic radius increases down a group as additional electron shells are present and atomic radius decreases across a period as the charge between nucleus and electrons increases as the proton number increases
Define ionic radius
The distance between the nucleus and most outer electron of an ion
How does ionic radius change for Cations
Ionic radius decreases as the atoms loses an entire energy level when ionizing
The radius increases down a group as there are more electron shells
The radius decreases across the group as the valency electron number remains the same but the proton number increases and the attraction is stronger
How does ionic radius change for anions across a period and group.
The radius increases down a group as there are more electron shells
The radius decreases across the group as the electron number remains the same but the electron number decreases and the attraction is stronger
How do melting points change down group 1 and 17. Explain why.
Melting points decrease down group 1 as metalic bonding strength decreases down the group as the ionic radius increases
Melting points increase down group 17 as intermolecular forces increase due to the repulsion of nuclei decreasing given increased ionic radius
How do first ionisation energy change down the group and across a period?
Values decrease down a group a the valency electron is further away from the positive nucleus
The values increase across a period as additional electrons are added to the electron shell increasing the attraction to the nucleus. Additionally if electrons are of opposite spin the ie will be lower as their will be repulsion between electrons
Define electronegativity
A relative measure of attraction between an atom and a shared pair of electrons when it is covalently bonded
How does electronegativity change across a period and down a group. Explain why
As the size of the atom increases the electronegativity decreases thus electronegativity decreases down a group and increase across a period
Define electron affinity
The energy change measured when one mole of electrons are added to an isolated atom in its gaseous states
Explain first and second electron affinity for oxygen
The first electron added has a negative vale for oxygen as the electron wants to gain another electron but adding a second electron requires energy as the atom is negatively charged and the repulsion must be overcome.
How does reactivity change in group 1 and why?
The reactivity increases down the group as the distance between nucleus and valency electron increases and thus attraction decreases allowing the electron to be lost easier
How does reactivity change down group 17 and why?
The reactivity decreases down the group as the distance between nucleus and valency shell increases and thus attraction decreases between nucleus and free electrons
Test for halide ions
The pressence of a halogen in a solution cam be detected by adding silver which will form a precipitate
Color of
Silver chloride
Silver Bromide
Silver Iodide
Silver chloride - white
Silver Bromide - cream
Silver Iodide - yellow
Define transition metal
An element that possess an incomplete d sub level in one or more of its oxidation states
Why isn’t Zinc a transition metal
Zn can from only two ions, Zn+1, and Zn+2 which all have a full d sub level
Properties of transition elements
-Catalytic properties
-Forms ligands
-Variable oxidation states
-Forms coloured compounds
-Magnetic properties
4 examples of catalysts
Iron in harbor process [Nitrogen + hydrogen –> ammonia] reversible
Vanidium (V) oxide in the contact process [sulfur dioxide + oxygen –> sulfur trioxide] reversible
Nickle in hydrogentaion reactions [ethene + hydrogen –> ethane]
Manganese (IV) with hydrogen peroxide [hydrogen peroxide –> water + oxygen]
Explain ferro-magnetism and provide three examples
This is when unpaired electrons (domains) align parrallel to each other regardless wether an external magnetic field is present.
Fe, Co, Ni
Explain paramagnetism
Electrons which are unpaired do not cancel out their spins. These spins will create a small magnetic field, and will line up in an electrical or magnetic field. The more unpaired electrons the more paramagnetic the complex will be.
Explain diamagnetism
When all the electrons in a transition metal complex are paired up the complex is said to be diamagnetic
What dictated wether a ligand complex with iron will be paramagnetic or diamagnetic?
If the ligand is low in the spectrochemical series it will split the 5 d oriibital only slightly allowing for electrons to occupy the split sub level producing paramagentism
If the ligand is high in the spectrochemical series it will split the 5 d oriibital only a lot, not allowing for electrons to occupy the split sub level producing diamagnetism as all electrons are paired
Define lignand
Ligands are neutral molecules or anions which contain a non-bonding pair of electrons.
How do complex ions form
Ligands are neutral molecules or anions which contain a non-bonding pair of electrons These electron pairs can form co-ordinate covalent bonds with the metal ion to form complex ions.
What factors affect the color of transition metal complexes?
- The nature of the transition element
-Oxidation state of transition metal
-The identity of the ligand
-The shape of the molecule or ion
-How much the d orbitals split
What is a coordination number in complex ions?
The number of lone pairs bonded to the metal ion in a complex ion.
Ex. [ Fe (CN)6 ] 3-
coordination number is 6
How does splitting of D orbitals occur and how does color come as a result?
All d orbitals are of equal energy. The d orbitals which lie ALONG the x-y and z axis are repelled by ligands causing the orbitals to split. Those (two) which lie along the axis go to a higher level and the remaining three go to a lower energy level.
Electrons are promoted by absorbing wavelength, and if they are promoted for example by red light, the color they will show is blue light as it is complementary.
What factors affect d orbital splitting in complex ions?
- The transition metal as the number of protons in the nucleus change
- Oxidation state of the metal as the number of electrons in the level will change
- The electron density of the ligand
How do complementary colors work?
If a white light is passed through a solution where the wavelength corresponding to the color red is absorbed than the observer will see the color which corresponds to the opposite wavelength of on the color wheel to red
What type of bonding is present in Silicon and Diamond
macromolecular covalent structure with very strong bonds resulting in very high melting point.
Why does Helium have a higher first ionisation energy than hydrogen even though the electron being removed has opposite spin repulsion?
Helium is a noble gas with a stable configuration
Why does Beryllium have a higher first ionisation energy than Lithium even though the electron being removed has opposite spin repulsion?
Beryllium has its electron removed from its fully filled 2S orbital, which is more stable than lithium’s partialy filled 2S orbital
How do we know which of two elements both showing paramagnetism will have a stronger magnetic field?
The more unpaired electrons there are in the complex the more paramagnetic the complex will be.
Why is zinc not considered a transition element?
Zn is not considered to be a transition element as it does not form ions with incomplete d-orbitals and all of its compunds are colorless
Why do different transition metals have different ligand colored complexes?
The amount that the d orbitals are split will determine the exact colour. Changing the transition metal changes the number of protons in the nucleus which will affect the levels.
Do anions have a larger or smaller radius than their atom and why?
Anions have a larger radius than there atoms as the number of electron-electron repulsion interactions that take place
