Fundamental Aspects of Chemistry Flashcards
Noble gases, ionic bonding, covalent bonding, electronegativity, polar bonds.
What is Helium used for?
As a pressurising agent for flight fluid systems.
What is Neon used for?
Neon lights.
What is Argon used for?
Creating an inert atmosphere needed in light blubs.
What is Krypton used for?
(Energy saving) bulbs.
What is Xenon used for?
Camera flashes.
What is Radon used for?
Cancer treatment.
Why are the Noble gases very stable and the most inert of all the elements?
Due to their electron configuration.
Most other gases are diatomic. Why are the Noble gases monatomic?
The Noble gases don’t need to gain/lose/share electrons so don’t normally form bonds with other elements.
How many electrons are in the valence shells of the Noble gases?
8 (except Helium).
What is the Lewis Octet rule?
The tendency of atoms to prefer to have 8 electrons in valence shell (highest principle quantum number/outermost shell of any atom).
Atoms form chemical bonds with other atoms when they haven’t got 8 electrons in their…
valence shell.
Why must atoms collide with each other to make chemical bonds?
Chemical bonds are made from electrons.
There are two types of electron (core and valence).
Which type take part in chemical bonding?
Valence electrons.
Which 2 main ways do atoms bond with other atoms?
Ionic and covalent bonding.
When atoms lose/gain electrons by reacting with other atoms they fulfil the octet rule to become ions.
Define an ionic bond.
The electrostatic attraction that forms between oppositely charged ions.
What are anions?
Negatively charged ions.
What are cations?
Positively charged ions.
Why do ionic compounds have a neutral charge?
The total charge from cations must equal the total charge from anions.
What is a binary compound?
Compound composed of only two different elements.
What giant 3D structures do ionic compounds form?
Ionic lattices.
How do generally s and d block elements (metals) end up in order to form an ionic bond?
Atoms lose electrons to have a positive charge = cations.
How do generally p block elements (non-metals) end up in order to form an ionic bond?
Atoms gain electrons to have a negative charge = anions.
Some groups of atoms behave as if they were a single ion.
How are they treated when in a compound?
As a single entity.
Name the following ions:
(PO4)^3-
(SO4)^2-
(CO3)^2-
(NO3)^-
(OH)^-
(NH4)^+
Phosphate
Sulphate
Carbonate
Nitrate
Hydroxide
Ammonium
To form a covalent bond atoms share electrons.
What is a covalent bond?
A shared pair of electrons between atoms.
How are covalent bonds represented?
As lines/wedges.
Atoms in a covalent bond both have full…
outer/valence shells.
Many elements are simple diatomics.
What are simple diatomics?
Exist as molecules (2 atoms joined by a covalent bond).
Give an example of atoms sharing more than one electron.
Nitrogen atom requires 3 electrons for a full valence shell.
Forms a diatomic nitrogen molecule with a triple covalent bond.
Why is hydrogen chloride special?
In its gaseous form = covalent but in aqueous form it ionises completely to give H+ and Cl- (hydrochloric acid).
What is the electronegativity of a an element dependent upon?
Its position in the periodic table.
When is the electronegativity of an atom high?
If the atom has a high nuclear charge, small atomic radius and low amount of shielding.
Whether a bond is ionic/covalent is determined by…
the electronegativity of the element.
Define electronegativity.
The power of an atom in a molecule to attract electrons towards itself.
An atom that pulls electrons strongly towards itself has a high…
electronegativity.
What kind of property is the Pauling Scale of Electronegativity?
Periodic property.
What are the units for the Pauling Scale of Electronegativity?
The values have no units.
Describe and explain what happens to the Pauling Scale of Electronegativity across a period.
Values increase.
Increasing nuclear charge causes atomic radius to decrease.
Similar shielding.
Describe and explain what happens to the Pauling Scale of Electronegativity down a group.
Values decrease.
More electron shielding.
Greater atomic radius.
How would you predict whether a bond is ionic or covalent?
- Calculate the difference in the values of
electronegativity of the two boning
elements. - If the difference in values is greater than
1.7, the bond is likely to be more ionic
OR - If the difference in values is less than 1.7,
the bond is likely to be more covalent.
Different electronegativities between atoms leads to a scale of bonding.
What would the values 2.1, 0.9 and 0 lead to state about each bond?
2.1 = ionic bond.
0.9 = polar covalent bond.
0 = covalent bond.
Which properties differ between ionic and covalently bonded compounds?
Boiling points, melting points, solubility in water, electrical conductivity.
Further covalent bonding:
In order to fill valence shells not all electrons need to covalently bond.
What are unbonded pairs of electrons called?
Lone pairs.
What is the bond called when lone pairs are shared with ions?
Dative covalent bonds (represented by an arrow).
