1.4 Bonding Flashcards
What is a chemical bond?
A force that holds together two or more atoms, ions, molecules or any combination of those.
What is ionic bonding?
Strong electrostatic forces of attraction between positive and negative ions. Bonding between metal and non-metal. (metal gives electron, non-metal receives electron so both atoms achieve full outershell)
What is covalent bonding?
Bonding between non-metal and non-metal only. (atoms join together to share electrons to achieve a full outershell)
There are no charges in covalent bonding
What is metallic bonding?
Bonding between positive ions and a sea of electrons.
What are the typical properties of metals?
Conduct electricity Conduct heat High melting points Malleable (can be bent into shapes) Ductile (can be drawn into wires)
What are the typical properties of non-metals?
Don't conduct electricity Don't conduct heat Low melting points Not malleable Not ductile
What is an ionic crystal?
A giant lattice (structure) held by electrostatic attraction of oppositely charged ions.
Why do ionic compounds have a high melting point?
Ionic compounds have strong electrostatic attration of oppositely charged ions. Therefore it requires a lot of energy to break the ionic bonds.
Where are the attractive forces in ionic bonding of two atoms?
Between oppositely charged ions
Between outer electron and nucleus of different ions
Where are the repulsive forces in ionic bonding of two atoms?
Between outer electron and outer electron (same charge, both -)
Between 2 nuclei
Between 2 same charged ions
Where are the attractive forces in covalent bonding of two atoms?
Between outer electron and linear nucleus
Where are the repulsive forces in covalent bonding of two atoms?
Between outer electron and outer electron
Between inner nucleus and inner nucleus
What are covalent compounds made of?
Simple molecules with WEAK forces between them but the covalent bonds are STRONG
What does the term ‘diatomic’ mean?
molecule consists of two same atoms.
What are the diatomic elements?
H₂, N₂, F₂, O₂, I₂, Cl₂, Br₂
What is coordinate/dative bonding?
A type of covalent bonding where both or more electrons in the bond are supplied by the same atom
e.g BF₃ (Boron fluoride)
NH₃ (Ammonia)
What does electronegativity mean?
The ability of an atom in a covalent bond to attract a shared pair of electrons
What’s the trend on electronegativity?
electronegativity increases from left to right across a period (increases up a group in a same period) in the periodic table and decreases down a group from group 7
electronegativity also decreases down the periods.
which atom has the greatest electronegativity?
Fluorine
Which atom has the least electronegativity?
Francium
Why the electronegativity of a fluorine atom is greater than oxygen atom?
Because fluorine has more protons than oxygen therefore it got a greater nucleus charge so it can attract electrons easier
Why the electronegativity of a fluorine atom is greater than chlorine atom?
Because chlorine is further down in the group than fluorine therefore it has a more filled electron shells. This means that there is more shielding of the nucleus and therefore the pull of nucleus to attract electrons is less.
What are the six most electronegative elements?
Fluorine, oxygen, nitrogen, chlorine, bromine and sulfur
What can be used to represent the charge on the electronegative atoms?
𝛿⁻ (delta minus)
What can be used to represent the atoms that are bonded to electronegative atoms?
𝛿⁺ (delta plus)
What are dipoles?
dipoles are formed when a covalent bond exists between atoms of differing electronegativity. The shared pair of electrons is displaced towards the more electronegative atom.
What is a polar molecule?
A molecule in which one end of the molecule is slightly positive, while the other end is slightly negative.
How are polar molecules formed?
The displacement of electron density makes the less electronegative atom slightly electron deficient (loss of electrons, 𝛿⁺) while the more electronegative atom has a slight excess of electron density (𝛿⁻) This charge separation creates an electric dipole.
What does polarity means?
Unequal sharing of electrons
Is carbon - hydrogen a polar bond?
NO, because the electronegativity of carbon and hydrogen are so similar that THEY ARE NOT considered as a polar covalent bond . SO NEVER PUT 𝛿⁻ OR 𝛿⁺ on a C-H bond!!!!!
Why polar molecules have a high melting point?
They have attraction between opposite charges therefore are harder to pull apart, so a lot energy are needed to break the polar covalent bond.
What are the melting points dependent on in covalent bonds?
how strong the forces between molecules.
If the force is weak, it’s easier to pull apart therefore less energy are needed to break the bond (low melting point).
If the force is strong, it’s harder to pull apart therefore more energy are needed to break the bond (high melting point)
What does polar bond arise means?
When the electrons are not shared equality in a covalent bond.
One of the atom exerts a stronger attractive force on the electrons than the other atom
Explain why hydrogen fluoride is classed as a polar molecule and describe how this polarity arises?
Hydrogen atom has a low electronegativity compared to fluorine atom therefore the charge separation causes the hydrogen fluoride to become a polar molecule. In the H-F bond, fluorine has the greater electronegativity therefore it pulls the shared pair of electrons more towards itself, causing unequal shared pair of electrons
Why water has a high boiling temperature of 100°C?
Oxygen atom is more electronegative than hydrogen atoms therefore it has the ability to pull electrons more towards itself. causing one end of the molecule slightly positive and the other end of the molecule slightly negative. The electrostatic attraction between negative and positive charges is strong as well as a great hydrogen bonds between water molecules therefore stronger intermolecular forces within the structure therefore a lot energy are needed to break the hydrogen bonds therefore it has a high boiling point.
