electron bonding and structure Flashcards
What is first ionisation energy
The energy required to remove one electron from each atone from 1mole of gaseous atoms to form 1mole of gaseous +1 ions
Successive ionisation energies.
The measure of energy required to remove each electron in turn
Second ionisation energy?
Energy required to remove one electron from each atom in one mole of gaseous atoms to form 1mole of +2 ions
What is plasma?
The mixture between positive ions and negative electrons
What does a large increase in successive ionisation energies show?
That the second electron has been removed from a different shell, closer to the nucleus and with less shielding than inner electrons
What is the filling order for shells?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d
What is a semi metal?
Displays properties of metal and non metal
What is periodicity?
The trend in properties repeated a cross a period
Describe the periodic trend in terms of electron configuration across the periodic table?
For each successive element there is one more electron in the outer shell
What is an example of a metalliod and why?
Silicon because it is shiny like a metal but it brittle and it conducts electricity but very poorly
What is the distinct change between group 4 and group 5 in both physical and molecular structure?
Giant structures to simple molecular structures
Strong forces to weak forces
Why is group 2 called the alkaline earth metals
All have hydroxides that are alkaline
What are group 2 general properties
High melting and boiling points
Low densities
FORM COLOURLESS COMPOUNDS
Why do first ionisation energies decrease down a group ?
Example?
- offsetting the nuclear charge is a greater distance from the nucleus and more screeningThe only factor left is the extra distance between the outer electron and the nucleus in
- sodium and lithium
In both Periods 2 and 3, although there are some fluctuations, the main trend is for first ionisation energy to increase across both periods. Explain why that is.
In Period 2, the outer electrons are all in 2-level orbitals, which are all at much the same sort of distance from the nucleus. They are all screened by the 1s electrons. As you go across the period, the number of protons in the nucleus increases, increasing the attraction on the 2-level electron which will be removed. In Period 3, the same thing is true, except that we are now talking about 3- level electrons, screened by 1s, 2s and 2p electrons. Because attractions increase, ionisation energy will also increase.
Using magnesium and beryllium as an example, explain why first ionisation energies in Period 3 are smaller than the corresponding ones in Period 2.
Magnesium’s electronic structure is 1s2 2s2 2p6 3s2 ; beryllium’s is 1s2 2s2.The magnesium’s first ionisation energy is less than beryllium’s because the electron being removed is in the 3-level rather than the 2-level, and so is further from the attraction of the nucleus.
Explain why the elements from scandium to copper have similar first ionisation energies.
The first electron to be lost from all of the d-block elements comes from the 4s orbital. The 3d orbitals lie slightly closer to the nucleus. As you add an extra proton to the nucleus, you also add an extra electron to the 3d orbitals. That more or less screens the effect of the extra proton.
What does a tetrahedral shape look like?
1 up
3 bottom
What six elements exist naturally as single unbounded atoms
The noble gases
What makes the noble gases so unreactive
- very stable outer shell of 8 electrons or 2 electrons
- two in s orbital and two each in 3p orbitals
What is the octet rule?
Unpaired electrons pair up by sharing or transferring electrons to form chemical bond
Results in each atom having the same electron config of a noble gas
Tendency to acquire this is octet rule
What is a compound
A substance formed from 2 or more chemically bonded elements in a fixed ratio usually shown by a chemical formula
What happens in ionic bonding
Electrons transferred from metal to non metal to form oppositely charged ions that attract
What happens in covalent bonding
Electrons shared between 2 non metals
What is an ionic bond
The electrostatic attraction between oppositely charged ions
What is the structure of a metallic bond and describe it
A giant ionic lattice: each ion surrounded by negative electrons forming a giant ionic lattice when in solid state
Why do ionic compounds have high melting and boiling points
Solids at room temp
Large amount of energy needed to break STRONG electrostatic forces that that hold oppositely charged ions together in lattice