Chemistry unit 6 Flashcards
What direction is a period?
The horizontal (left to right)
What direction is a group/family
Vertical
What is atomic radius/ Atomic Radii
The total distance from the nucleus of an atom to its outermost orbital
What is the pattern of Atomic Radius?
It decreases from left to right (due to increased charge on the nucleus)
It increases from top to bottom in a family (due to the shielding effect and larger orbitals)
What is electronegativity
Electronegativity is a measure of how strongly an atom attracts a bonding pair of electrons .
What is the electronegativity trend
It increases from left to right
It decreases from top to bottom
What is ionization energy
It is the energy needed to remove an electron from a neutral atom
What is the ionization energy trend?
It increases from left to right (period)
It decreases from top to bottom (family)
What is the difference between the 1st and 2nd ionization energy
The 1st is the energy needed to remove the first electron from a neutral atom.
The 2nd is the energy needed to remove the second electron. *(and so forth)
Why does the difference between 1st and 2nd ionization energy vary so much?
The 2nd ionization energy is always gonna be larger because it requires more alot more energy to remove an electron from a cation than from a neutral atom.
What is electron affinity?
Electron affinity is how badly a neutral atom wants to gain electrons.
What is the electron affinity trend?
It increases from left to right
It decreases from top to bottom
What is shielding?
Shielding is when the inner electrons act as a shield that prevents outer electrons from feeling an effective nuclear charge.
What are intramolecular forces?
Forces within a molecule or ionic compound that keep the molecule together.
Ex. Bonds between atoms
What are intermolecular forces?
The attraction between molecules or ions and molecules. IN A SOLID OR LIQUID STATE.
They determine many of the physical properties of a substance.
Which is stronger Intramolecular or Intermolecular?
Intramolecular - strong
Intermolecular - weak
What do atoms valence shells want
They want to achieve a full valence shell
For ionic bonding how does the electron configuration change?
The arrow from the atom that is loosing an electron must go to the atom that is gaining an electron
In covalent bonding how does the electron configuration change?
The two arrows come together in the middle to show that they are sharing.
What is a polar covalent bond?
It is when electrons are shared unequally between two atoms.
When does polar covalent sharing occur?
When the electronegativity difference is between 0.5 and 1.7 *(or 2.0 if it is only non metals)
What does polar covalent sharing result in?
Dipoles
What are dipoles?
It is when a molecule has a partially positive and a partially negative end (poles).
What are the steps for drawing Lewis diagrams for simple molecules?
Step1: Count valence E-
Step2: Determine the central atom.
Step3: Draw single bonds to the central atom.
Step4: Place remaining e- as lone pairs.
Step5: Turn lone pairs into double or triple bonds to give every atom a full valence shell.
Step6: Check period 3 or higher central atoms for a formal charge of 0.
When writing Lewis diagrams for ionic compounds how should they be arranged?
Brackets around dot structure with the charge next to them
negative next to positive.
How to represent the dipoles in lewis structures
By using an arrow with a plus on one end
The + represents the slightly more positive pole and the arrow represents the slightly more negative.
What does adding an electron (anion) do to the ionic radius?
Makes the atom bigger.
What does taking away an electron (cation) do to the ionic radius?
Makes the atom smaller.
What are the three elements that have an exception to the octet rule?
Be, B, and Al.
How many electrons does Be need to be satisfied?
Only 4.
How many electrons does B need to be satisfied?
Only 6.
How many electrons does Al need to be satisfied?
Only 6.
Why do Be, B, and Al not require a full octet?
Because by having incomplete octets they avoid having any formal charges.
How many electrons does H need to be satisfied?
Only 2.
Which 3 trends all go up from bottom left corner to top right corner?
*Increase left to right and decrease top to bottom
1) ionization energy
2) electron affinity
3) electronegativity
Which 1 trend goes up from top right corner to bottom left corner?
*Decrease left to right and increase top to bottom
Atomic Radius (Radii)
How to know how many bonds different elements will make?
Bonds + VE = 8
Ex: N=5 VE so it will have 3 bonds.
Why do elements in the same family have similar properties?
Because they have the same valence electron number.
What causes the atomic radius trend?
It decreases left to right because atomic # gets bigger (more protons) which results in a stronger nuclear attraction
It increases from top to bottom of the periodic table because more shells are added and more shielding so less nuclear attraction
What causes the ionization trend?
It increases left to right because as the atomic radius decreases the electrons are more strongly pulled towards the nucleus therefore it is more difficult to remove outermost electron.
It decreases from top to bottom because the electrons have less shielding and are further away and less pulled towards nucleus so it is easier to remove outermost E-
What causes the electronegativity trend?
It increases as you move from left to right due to an increasing nuclear charge.
It decreases as you move down because of the larger atomic radius.
What causes the electron affinity trend?
It increases left to right because of the increasing nuclear charge.
It decreases top to bottom due to a larger atomic radius.
What is vesper theory?
Vesper theory states that the valence e- pairs in a molecule arrange themselves around central atom so that the repulsion between their negative charges is as small as possible.
What are the two types of domains?
Lone pairs - the non bonding domains
Bonds - bonding domains
Main reason VESPER theory was created
to help predict the shapes of molecules
What causes molecules to take on different shapes?
The electrons and nuclei go into positions that minimize repulsion and maximize the attraction.
What are the three types of repulsions that occur in an atom
1) Lone pair - Lone pair
2) Bonding pair - Bonding pair
3) Lone pair - Bonding pair
Why is it important to know the shape of molecules?
It can determine what properties it has and its uses.
**Also important for polarity.
When is the bond polar? EN
when electronegativity difference is between 0.4 and 1.8
When is the bond non polar? EN
when electronegativity difference is less then 0.4
When is the bond ionic? EN
when electro negativity is bigger than 1.8
When do you know if the vesper shape is polar
when charges are asymmetrical and the bonds are also polar
When is a molecule non polar?
when the molecule is symetric
non polar bonds
electronegativity vectors cancel
Steps to determining the vesper shape:
1) Draw Lewis structure
2) Determine central atom
3) Determine the # of domains
4) Use chart to find shape
What are the four types of intermolecular forces?
Hydrogen bonds
Dipole - dipole
London forces
Ion - dipole forces
What are dipole-dipole forces between
Electrostatic attractive force between two polar molecules
what is a weak dipole?
EN between 0.1 and 0.4
What is a strong dipole
greater than 0.4
Why do dipole dipole have higher melting and boiling points
because adjacent polar molecules attract resulting in higher melting and boiling points
What are hydrogen bonds between
Electrostatic attractive force between between O-H, N-H, F-H and a lone pair on an O F or N
What is hydrogen bonding
essentially a stronger version of dipole dipole force
example of hydrogen bonding
DNA!
What are london forces between
Weak force that holds non polar molecules together in LIQUID and SOLID
How does london forces work
when the electrons move to a temporary position that gives dipoles for a short period of time
What is an Electrostatic attractive force?
These are forces that can pull or push objects without touching them.
What are ion dipole forces between
An ion and a neutral molecule thats polar
What are ion dipole forces common
In SOULUTIONS!
Does atomic radius increase or decrease as you go down a group/family on the periodic table?
Increase
what is an ion
A partice, atom , or molecule that has an electrical charge from gaining or loosing e-(s)
what is group 1 called
alkalai metal
What is group 2 called
alkaline earth metals
What is group 3 - 12 called
transition metals
what is group 17 called
halogens
what is group 18 called
Noble gases
what is group 16 called
oxygen family (chalcogens)
what is group 15 called
pnitcogens.
what is true for the elements within any group
similar properties
