Topic 3: Periodicity Flashcards
What is the periodic table arranged according to
Increasing atomic number
What does period number represent
The number of energy levels (shells)
What is group number
the number of valence electrons
Name for group 1, 17 and 18
Alkali metals, halogens and noble gases
What are lanthanoids on the periodic table
La to Lu
Actinoids on periodic table
Ac to Lr
What properties do metalloids have
Those intermediate between those of a metal and a non-metal
Chemical and physical properties of a group
Are similar
How to find atomic radius and its trend
Half of the distance between the nuclei of two bonded atoms of the same element
radius increases down a group because outermost electrons are in higher energy levels
radius decreases across period because there are an increasing amount of protons and positive charge - attracts energy level closer
Ionic radius trend
Important to consider cations vs anions
Groups 1,2,3 that form cations have smaller radius because they have fewer electrons then protons causing the inward pull to be stronger, ion is smaller than parent atom because energy shell has decreased by one
Groups 5, 6, 7 that form anions have bigger ionic radius because they have more electrons than protons + gained an energy shell
Melting points across period 3
Na, Mg and Al exhibit metallic bonding –> which strength increases as the number of valence electrons increase
Si –> is a giant covalent structure - so extremely high melting point
P4, S8, Cl 2 are simple molecular structures with weak intermolecular forces of attraction, held together by LDF so the larger the atom the higher the mp
noble gases have very weak forces of attraction
Melting point trend down group 1 and group 17
Melting point decreases down group 1, atom becomes larger so strength of metallic bond decreases
Increase down group 17 - intermolecular forces increase down the group (van der waal forces increase with greater atom and more electrons0
First ionization energy
Amount of energy required to remove the first electron from an atom in the GASEOUS STATE
First ionization energy trend
Decrease down group because greater atomic mass means less hold on the electrons, increase across period because more protons and the extra electrons are added to the same shell
Electronegativity
measure of the attraction an atom has for the shared pair of electrons in a covalent bond
Electronegativity trend
Decreases down group and increases across period due to increasing protons (F, N and O are the most electronegative) (wow the hydrogen bonding ones)
First electron affinity
energy change when an electron is added to an isolated atom in the gaseous state
Values are negative for the addition of the first electron because they want it (exothermic)
the more it wants it the more energy is released
Why is group 1 called alkali metals
They all react with water to form an alkali solution of the metal hydroxide and hydrogen gas
Chemical properties of group 1
They react by losing their outer electron to form metal ion, are good reducing agents, reactivity increases down group because less energy holding onto the elecctrons.
Chemical properties of group 17
React by gaining one more electron to form halide ions, good oxidizing agents, reactivity decreases down group because less pull inwards
how to detect halide ions in solution
add silver nitrate solution, forms precipitate of silver halide and can be distinguished by their colour, reacts with light to form silver metal. is the basis of old fashioned film photography.
how to distinguish metal from non metals
through chemical properties, metal oxides tend to be basic, whereas non metal oxides are acidic
