Valence And Ionic & Covalent Bonds Flashcards
Define bond.
Forces that hold atoms together.
Define covalent bond.
A bond where two atoms share electrons.
Define ionic bond.
A bond between a metal and non-metal.
Define electronegativity.
An atoms ability to attract electrons in a chemical bond.
Define empirical formula.
The simplest ratio of atoms.
Why don’t noble gases have electronegativity?
Because they have a full outer shell.
Define ΔEN.
Difference in electronegativity.
To predict what type of bond will form you need to work out ΔEN. How is this done?
EN(Element 1) - EN(Element 2) = ΔEN
What is the ΔEN value for ionic bonds?
More than 2.1
What is the ΔEN value for polar covalent bonds?
0.4 to 2.1
What is the ΔEN value for non-polar covalent bonds?
Less than 0.4
Define δ-
It means delta negative and gain of electron density.
Define δ+
It means delta positve and loss of electron density.
Define deshielding.
When the electrons aren’t shared equally as a polar covalent bond is formed.
What does this diagram represent?
A polar covalent bond has formed. The arrow represents a dipole directing to the more electronegative element.
What are the three rules for drawing Lewis structures?
- Count the valence electrons (number of outer electrons).
- Use two electrons to form a covalent bond.
- Use remaining electrons to yield full valency for all atoms.
Define duet rule.
Full valency of the first shell, which is two electrons.
Define octet rule.
Full valency of the outer shell, which is eight electrons.
How many bonds can Hydrogen make?
One.
The octet rule applies to which four elements?
Carbon, Nitrogen, Oxygen and Fluorine as they cannot exceed eight electrons.
What four elements can have less electrons than the octet rule?
Beryllium, Magnesium, Boron and Aluminium.
What two elements can have the same or more electrons than the octet rule?
Phosphate and Sulphur.
Define structural isomers.
Same molecular formula, but different gross connectivity.
Define geometric isomers.
Same gross connectivity, but different orientation in space due to no rotation about double bond.
Define saturated.
CnH2n+2
Define unsaturated.
CnH2n
Define valency.
The potential of an atom of an element to combine with other atoms measured by the number of electrons which an atom will give, take or share to form a chemical bond.
Define postive valence.
Valence electrons are donated.
Define negative valence.
Valence electrons are accepted.
Define ionisation energy.
The energy required to remove a valence electron from a given atom.
If an atom has high ionisation energy, are the valence electrons easier or harder to remove?
Harder.
If an atom has small ionisation energy, are the valence electrons easier or harder to remove?
Easier.
How many times stronger is a covalent bond than an ionic bond?
5 to 20 times stronger.
What do ionic bonds exist as at the molecular level?
Crystal lattice.
What percentage of cells are water?
70%.
Define bond length.
The distance at the lowest energy point is the separation between the atoms at which their attraction is maximal.
Who is regarded as the founder of modern Biology and Chemistry?
Linus Pauling.
Who developed the concept of the “chemical bond” and “molecular biology” in the 1940’s?
Linus Pauling.
