ions: electron configurations and sizes (3.3) Flashcards
What does the electron configuration of two non-metals reacting look like?
Since the atoms of the non-metals are identical, they are forming a covalent bond. This means the electrons are shared by the non-metals in a way that completes the valence electron configurations of both atoms. This way, both atoms are capable of being written in noble gas shorthand.
What does the electron configuration of a non-metal and metal reacting look like?
Since the atoms of the metal and non-metal are different, they are forming an ionic bond. This means that electrons are transferred amongst atoms to form ions and in turn, the valence electron configuration of the NONMETAL can be written in the configuration of the next noble gas as long as the valence shells/orbitals of the METAL are discarded/emptied.
Ex: Ca (metal) + O (non-metal)
Ca + O —> Ca^2+ + O^2-
Oxygen has a higher electronegativity than calcium so electrons from calcium will go to Oxygen to make calcium cations and oxygen anions.
Look at the electron configurations for both atoms and you will see that Oxygen only needs 2 more electrons to fill its 2s, 2p valence orbital before it achieves noble gas configuration of Neon.
For calcium to achieve the noble gas configuration of Argon, it needs to lose 2 electrons. So, do an electron transfer! Give two electrons to oxygen to make it O^2- (isoelectronic to neon) and take two electrons from calcium to make it Ca^2+ (isoelectronic to argon)
What do we have to assume about chemical compounds?
They are electrically neutral - they carry the same number of positive and negative charges.
Which ions of Sn (tin) are exceptions to the rule about common ions with noble gas confirmations amongst groups 1-3 and 6-7?
Sn^2+ and Sn 4+. There are no simple explanations for why tin always forms those ions, just remember them.
Which ions of Pb (lead) are exceptions to the rule about common ions with noble gas confirmations amongst groups 1-3 and 6-7?
Pb^2+ and Pb^ 4+. There are no simple explanations for why lead always forms those ions, just remember them.
Which ions of Bi (bismuth) are exceptions to the rule about common ions with noble gas confirmations amongst groups 1-3 and 6-7?
Bi^3+ and Bi5+. No simple explanations as to why this occurs, it just does.
Which ions of Th (thallium) are exceptions to the rule about common ions with noble gas confirmations amongst groups 1-3 and 6-7?
TI^+ and TI3+. No simple explanation as to why this occurs, it just does.
When ions are isoelectronic, what can you assume about them?
That they have the same number of electrons.
Why are anions bigger than their parent/neutral atoms?
Negative ions, or anions, are basically neutral atoms with additional electrons and that addition of electrons creates a bigger atomic radius, which is bigger than the neutral atom’s atomic radius
What happens to the size of an ion as you down the group of the periodic table?
It increases as you do down a group.
What happens to the size of an ion as you go across the period of the periodic table?
It’s tricky because the left side of the period doesn’t have an affinity for electrons - it forms cations - while the right side of the period has a strong affinity for electrons - so much so that it forms anions. So ion size differs across the table because it contains both elements that give up electrons to form positive ions and take electrons to form negative ions.
What happens to the size of isoelectronic ions when the effective nuclear charge increases?
It gets smaller when the effective nuclear charge increases because more protons result in a stronger, overpowering attraction to electrons, resulting in a decrease of atomic radius and a smaller ion. Think of it this way: anytime an atom has more protons than electrons, it’s more likely to form a positive ion (cation) and cations tend to be small.
What are the sizes of the following isoelectronic ions? List in order of decreasing size.
Sr2+-, Br-, Se2-,
Rb+
The ion with the highest nuclear charge is Sr2+ (The highest positively charged ion) so it is the smallest ion because it’s the smallest cation on the block. Go backwards from there on the periodic table.
The ion with the lowest nuclear charge is Se2- (the highest negatively charged ion) so it is the largest ion because it is the largest anion on the block.
Se2-+, Br-, Rb+, Sr^2+
