2.4 - Electrons, bonding and structure Flashcards
Define the term ‘orbital’ ?
Orbital - A region of space about the nucleus holding up to 2 electrons with opposite spins
What are the different types of orbitals ?
s, p, d, f
What is the shape of s orbitals ?
Spherical
What is the shape of p orbitals ?
Dumbbell-shaped
What is the number of orbitals in the s, p, d and f sub-shells ?
- s = one orbital ( two electrons )
- p = three orbitals ( six electrons )
- d = five orbitals ( ten electrons )
- f = seven orbitals ( fourteen electrons )
Do you know how to write electron configuration of atoms and ions ?
Yes
What are the rules for how shells are occupied by electrons ?
- The orbitals fills from the lowest energy levels
- The 4s orbital fills up before the 3d orbital
- The 4s orbital loses electrons first before the 3d orbital
Do you know how to write electron configuration using boxes ?
- Electrons will prefer to occupy orbitals on their own unless that option is unavailable
- Yes…
What are the exceptions to the rules of electron configuration ?
- Chromium and Copper
- The 4s orbital is occupied by one electron and is not completed as the 3d orbital is filled
Write the electron configuration for chromium and copper ?
- Chromium = 1s² 2s² 2p⁶ 3s² 3p⁴ 4s¹3d⁵
- Copper = 1s² 2s² 2p⁶ 3s² 3p⁴ 4s¹ 3d¹⁰
Define the term ‘ionic bond’ ?
Ionic bond - The strong electrostatic attraction between oppositely charged ions
What is the structure of ionic compounds ?
- They have a Giant Ionic lattice structure
- Each ion is surrounded by oppositely charged ions held together by strong ionic bonds
- The regular cubic arrangement gives the crystal its cubic shape
Explain the structure of an ionic compound such as sodium chloride ( NaCl ) ?
- Each positive sodium ion is surrounded by six negative chlorine ions forming a giant ionic lattice
- The regular cubic arrangement gives the crystal its cubic shape
Draw a diagram representing the structure of an ionic compound ( eg. NaCl ) ?
What are the physical properties of ionic compounds ?
- High melting/ boiling point
- Only conducts electricity when molten/ solution
- Brittle
- Soluble in polar solvents ( eg. Water )
Explain why ionic compounds have a high melting/ boiling point ?
Strong ionic bonds/ electrostatic attraction between oppositely charged ions require a lot of energy to break resulting in a high melting/ boiling point
Explain why ionic compounds can only conduct electricity when molten/ solution ?
Ions are mobile when an ionic compound is molten/ solution and therefore carry a charge. Ions are not able to move when solid.
Explain why ionic compounds are brittle ?
Applying a force causes like charged ions to align and therefore to repel
Explain why ionic compounds are soluble in polar solvents ?
Polar solvents such as water can often dissolve ionic compounds
Do you know how to draw dot and cross diagrams for ionic compounds ?
Yes
Define the term ‘covalent bond’ ?
Covalent bond - The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Define the term ‘dative covalent bond’ ?
Dative covalent bond - A covalent bond where both of the electrons come from the same species/ atoms
Do you know how to draw dot and cross diagrams for covalent bonding ?
Yes
What are double or triple covalent bonds ?
- A double covalent bond is two shared pair of electrons
- A triple covalent bond is three shared pair of electrons
Do you know how to draw dot and cross diagrams to represent multiple and dative covalent bonding ?
Yes
What is another name for a ‘dative covalent bond’ ?
A co-ordinated bond
How are ions formed ?
- Metal atoms lose electrons to form positive ions ( cations )
- Non-metal atoms gains electrons to form negative ions ( anions )
What does average bond enthalpy mean in regards to covalent bond strength ?
The higher the average bond enthalpy, the greater the strength of the covalent bonds
Define the term ‘electronegativity’ ?
Electronegativity - the ability of an atom to attract the electrons in a covalent bond
What are the factors affecting electronegativity ?
- Nuclear Charge
- Atomic Radius
- Shielding
Explain how nuclear charge affects electronegativity ?
- As the number of protons increases in the nucleus, the greater the nuclear charge
- This leads to stronger attraction between the nucleus and bonding pairs of electrons leading to an increase in electronegativity
Explain how atomic radius affects electronegativity ?
- As the atomic radius decreases, the distance between the nucleus and bonding pairs of electrons decreases
- This leads to stronger attraction between the nucleus and bonding pairs of electrons leading to an increase in electronegativity
Explain how shielding affects electronegativity ?
- As the number of electrons increases, the number of inner electrons shells and therefore shielding increases
- This leads to weaker attraction between the nucleus and bonding pairs of electrons causing the electronegativity to decrease
What is the trend in electronegativity down the group ?
As you go down the group, the electronegativity decreases
What is the trend in electronegativity across the period ?
As you go across the group, the electronegativity increases
Explain why electronegativity decreases down the group ?
- The atomic radius increases due to an increased number of electrons shells
- The shielding increases due to an increased number of electrons
Explain why electronegativity increases across the period ?
- The nuclear charge increases due to more protons
- Atomic radius decreases due to more protons in the nucleus
- The shielding stays the same as all elements are in the same period
Explain how atomic radius decreases across a period ?
- As you go across a period, the number of protons in the nucleus increases causing nuclear charge to increase
- This means there is a greater attraction force between the nucleus and electrons
- This means electrons within shells are held closer to the nucleus which decreases the atomic radius
