Chemical Bonding Flashcards
What is the direction of the trend of atomic radius
Down a group: increases atoms
Across a period: decreases size
Explain the atomic radius trend
Down a group: Valence electrons are found in energy levels that are further from the nucleus. The inner electrons FORMS A SHIELD, meaning that the outermost electrons are not attracted strongly to the nucleus.
Across a period: the number of protons increases. This increases the attractive pull between the nucleus and its electrons.
What is the direction of the trend of ionization energy
Down a group: Ionization energy decreases
Across a period: Ionization energy increases
What is ionization energy
The amount of energy required to remove an electron to form a chemical bond.
Explain the ionization energy trend
DOWN A GROUP: decreases due to electron shielding
ACROSS A PERIOD: increases due to increasing nuclear charge and its attraction to the electrons.
NOBLE GASES: have the highest ionization energies as their valence shells are full.
What is the direction of the trend of electronegativity
Down a group: Decreases
Across a period: increases
Noble gases DO NOT have electronegativity values because they generally don’t form bonds.
What is electronegativity
Is a measure of how willingly an atom can attract a bonding pair of electrons. (an atoms ability to gain electrons)
Name the exceptions to the Octet Rule
- To few electrons: Be satisfied with 4e-, B satisfied with 6 e-
- Odd number of electrons: Atoms in molecules with odd numbers of electrons, such as NO and NO2, cannot satisfy the octet rule
- Too many electrons: Elements in period 3 or higher, such as S and P have unoccupied d orbitals which can hold up to 10 e-, beyond the 8 usually held in valence shell.
- Coordinate covalent bonding: Sometimes the covalent bond can be formed by sharing two electrons donated by a single atom, as in ammonia or aluminum chloride.
What is electric repulsion
electrons try to stay as far away as possible from each other
What does VESPR stand for
Valence Electron Shell Pair Repulsion
What does VESPR do
-predicts shapes of molecules based on electron pairs repelling
-based on lewis structures
How many VESPR shapes are there
7
Name each VESPR shape
- Linear: 1 or 2 bonded electron pairs, 2D, ex) BeCl2 or HF
- Trigonal Planar: 3 bonded electron pairs, 2D, ex) BF3
- Tetrahedral: 4 bonded electron pairs, 3D, ex) CH4
4.Trigonal Pyramidal: 3 bonded electron pairs + 1 lone pair, 3D, ex) NH3
- Bent: 2 bonded electron pairs + 2 lone pairs, ex) H2O
- Trigonal Bipyramidal: 5 bonded electron pairs, 3D, ex)PF5
- Octahedral: 6 bonded electron pairs, 3D, ex) SF6
What did Bohr’s model focus on
Electrons
Explain the theory of Bohr’s model (hint: 4 points)
-neutrons and protons occupy the nucleus
-electrons move with constant speed in fixed orbits around the nucleus
-each electron has specific amounts of energy
-If an atom gains or loses energy, the energy of the electrons can change
What are energy levels (hint: 3 points)
-The possible energies that electrons in an atom can have
-can only move in whole increments
-the lowest step is ground state
what is the evidence or energy levels
emission spectrum: the type of visible light given off shows the different energy levels
Continuous Spectrum
Objects at high temperature emit a continuous spectrum when viewed through a diffraction grating. One continue light.
Line Spectrum
Sample of an INDIVIDUAL (pure) element is heated, and the emitted light passed through a diffraction grating, only a few narrow lines are observed. There’s space between the lines.
Explain how line spectra supported Bohr’s understanding of the atom.
- energy levels
-different colours of light support that there are many energy levels possible
-shows that electrons move up and down levels
Electron Cloud model
-used the work of Broglie, Schrödinger, and Heisenberg to understand the need for probability
-based on wave function and probability
-is a visual for the most likely locations for the electrons in an atom
-represents all the orbitals in the atom
-3D
What is an orbital
-is a region of space around the nucleus where an electron is likely to be found
-orbitals can overlap
-electrons can move into different orbitals by absorbing/emitting energy
-each orbital has only 2 e-
How do you find the number of protons, neutrons and electrons in atoms
Protons: atomic number
Electrons: = protons
Neutrons: Atomic mass-protons
WHEN CALCULATING ELECTRONS FOR IONS CONSIDER ITS CHARGE!!! DID IT GAIN OR LOSE ELECTRONS?
What is electron configuration
-How electrons are arranged in orbitals
-is important because it determines the chemical behaviour of every element
