Chemistry basics Flashcards
What defines an element?
The number of protons in the nucleus of its atoms
What is the atomic number?
The number of protons in the element
What is defined as the number of protons in an element’s atoms?
The atomic number
What is the main unit of order in the periodic table?
The atomic number
What does Z refer to in chemistry?
The atomic number
What is the symbol for the atomic number?
z
Why don’t electrons stick closely next to an atom’s protons?
They have high velocity
What does mass refer to?
The amount of something and its inertia
What is defined as the amount of something and its inertia?
Mass
What is measured in grams and kilograms?
Mass
What are example measurements of mass?
grams, kilograms
What is weight?
Weight refers to a force - how much gravity is pulling on an object
What is defined as the force of gravity pulling on an object?
Weight
How is weight measured?
In Newtons
What is measured in Newtons?
Weight
In space, you have ____ but not ____
mass, weight
What is AMU short for?
Atomic mass unit
What is an atomic mass unit?
A very small fraction of a gram, defined as one-twelfth of the mass of a carbon 12
What is the unit of measurement of mass in chemistry?
Atomic mass unit
Does the atomic mass unit refer to mass or weight?
Mass
What is the weighted average of the atomic masses of all an element’s isotopes found on Earth?
The atomic weight
What is atomic weight?
The weighted average of the atomic mass of all the isotopes of an element found on Earth
Does atomic weight refer to weight or mass?
Mass
In this fictional element from the periodic table, what does the number 14 refer to?
The atomic number - the number of protons in the nucleus
In this fictional element from the periodic table, what does the number 29 refer to?
The atomic weight - the weighted average of the atomic masses of all the element’s isotopes as present on Earth
In this fictional element, what does the number 29 refer to?
The mass number - the combined protons and neutrons in this isotope of the element
In this fictional element, what does the number 14 refer to?
The atomic number - the number of protons in this element
What is an alternate name and notation for an AMU?
Da, or Dalton
What is a Dalton?
Another name for atomic mass unit
What number is refered to by a mole?
6.022 x 1023
What measure do we use to translate bewteen AMUs and grams?
The mole
How was Avogadro’s number decided upon?
The number of Carbon 12 atoms in 12 grams of Carbon
What is the significance of the number of Carbon 12 atoms in 12g of Carbon?
This corresponds to Avogadro’s number, the number referred to by a mole - 6.022 X 1023
What’s the easiest way to figure out the mass in grams of one mole of an element?
It is the same as that element’s atomic weight
What is an isotope?
Isotopes are atoms of the same element with different numbers of neutrons in their nuclei.
What is the name for atoms of the same element which have different numbers of neutrons in their nuclei?
Isotopes
Isotopes will have the same ____ number but different ____ numbers
atomic, mass
What does mass number refer to?
The combined number of protons and neutrons in the atom
In chemistry, what does A refer to?
The mass number
How is mass number denominated?
A
What is this?
Protium - the most common isotope of hydrogen
What is deuterium?
An isotope of hydrogen with a neutron and a proton in the nucleus
What is the name of the isotope of hydrogen with a neutron and a proton in the nucleus
Deuterium
What is this:
Tritium - an isotope of hydrogen with two neutrons in its nucleus
What is tritium?
The isotope of hydrogen with two neutrons in its nucleus.
What do you call an atom which has a different number of electrons than protons?
An ion
What is an ion?
An atom which has a different number of electrons and protons
Hydrogen peroxide contains 2 hydrogens and 2 oxygens. What is the empirical formula for hydrogen peroxide?
HO
What is the empirical formula for water?
H2O
What does the empirical formula for a compound indicate?
The simplest ratio of elements contained in a molecular compound, but not the actual number
Which type of formula indicates the simplest ratio of elements contained in a molecular compound?
The empirical formula
Hydrogen peroxide contains 2 hydrogens and 2 oxygens. What is the molecular formula for hydrogen peroxide?
H2O2
What is the molecular formula for water?
H2O
Name each of these formula types for hydrogen peroxide
Structural
Molecular
Empirical
What determines the net charge of an ionic compound?
The net charge is always zero
When is the systemic name of a compound used?
When an ionic compound contains a polyvalent cation.
What is chromium(II) chloride an example of?
The systemic name for an ionic compound (used where a polyvalent cation is present)
What does the II in chromium(II) chloride refer to?
The magnitude of the charge on the chromium cation.
What is a polyvalent element?
It is an element that can combine using different numbers of electrons (thereby showing different valences)
What two types of names are sometimes used in ionic compounds which contain polyvalent elements?
Systemic name: e.g. copper (II)
Common/trivial name: e.g. cupric
What is the name of the process which uses a balanced chemical equation to calculate ratios of reactants and products?
Stoichiometry
Define stoichiometry
The process of using a balanced chemical equation to calculate the ratios of reactants and products
What do you call the numbers used to balance chemical equations?
Stoichiometric coefficients
What are stoichiometric coefficients?
The number used to balance a chemical equation, which can be interpreted as moles
What do mole ratio, stoichiometric factor, and stoichiometric ratio all refer to?
The ratio that indicates the relative proportion of chemicals in a reaction
What are three names for the ratio which indicates the relative proportions of chemicals in a reaction?
Mole ratio, stoichiometric factor, stoichiometric ratio
What is the first step in stoichiometry?
Balance the equation
How is the limiting reagent defined?
If there is proportionally less of one reagent than another required for a reaction to take place, that reagent is called the limiting reagent.
What does the molecular mass percentage tell us?
The percentage of a molecule’s mass contributed by each of its component elements
What does redox refer to?
Oxidation-reduction
What are the two mnemonics for remembering the definition of oxidation and reduction?
LEO the lion says GER
LEO: Losing electrons = oxidation
GER: Gaining electrons = reduction
OIL RIG
OIL: Oxidation is losing
RIG: Reduction is gaining
What is oxidation state?
The hypothetical charge an element in a compound would take if all bonds were 100% ionic
What are the rows of the periodic table called?
Periods
What are the columns of the periodic table called?
Groups
What links elements in a group on the periodic table?
They all have similar chemical properties (e.g. reactivity), and tend to have the same number of valence electrons (electrons in their outermost shell)
How are the alkali metals similar to one another?
They are all highly reactive, and are therefore not found in their pure state in nature
What is contained in Group 1 of the periodic table?
The alkali metals, plus hydrogen
Where are the alkali metals found in the periodic table?
Group 1
What is found in Group 2 of the periodic table?
The alkaline earth metals
Where are the alkaline earth metals found in the periodic table?
Group 2 or 2A
What are 6 properties of metals?
- Solid at room temperature (except mercury)
- Malleable (not brittle, can be shaped)
- Ductile (can be drawn into wires)
- Opaque
- High density
- Good conductors of heat and electricity
What is found in group 17 (or 7A) on the periodic table?
Halogens
Where are halogens found in the periodic table?
Group 17 or 7A
How do halogens tend to be similar to one another (4 ways)?
- Colourful
- Corrosive
- Reactive
- “Salt former”
What is found in group 18 or 8A in the periodic table?
The noble gases
Where can you find the noble gases in the periodic table?
Group 8A or 18
How are noble gases similar to one another (2 ways)?
Colourless and unreactive
Where would you find metalloids on the periodic table?
At the zigzag line that divides the metals and non-metals
What do the elements in a period have in common?
They all have their valence electrons in the same shell/energy field
Chlorine’s electron configuration is:
1s22s2p63s2p5
How many valence electrons does it have?
Seven
Remember: All electrons in the outermost energy field are counted as valence electrons regardless of which orbital they are in
What does the numbering pattern 1A-8A refer to in the periodic table?
The main groups
What do the element blocks in the periodic table refer to?
Elements in the same block tend to have their differentiating electron in the same atomic orbital
What are the names of the element blocks of the periodic table?
s, p, d, f
How is a transition element defined?
These are elements which have an incomplete d-orbital
How many electrons can be contained in a d-orbital?
10
What molecule is this?
Ethene
Remember:“Eth-“ means two, and “-ene” means at least one double-bond
Draw the dot structure for ethene
Remember: “Eth-“ means two, and “-ene” means at least one double bond
What is the name of this molecule?
C2H2
Ethyne
Remember: The dot structure must look like this. “Eth-“ means two and “-yne” means at least one triple bond
How would an electron shift from one orbital to another?
If it gained or lost energy
What do s, p, d, and f refer to?
Subshells
Each orbital can fit ___ electrons
2
How many electrons can the s subshell fit?
2
How many electrons can the p subshell fit?
6
How many electrons can the d subshell fit?
10
How many electrons can the f subshell fit?
14
What do (as examples) px and dxz refer to?
Orbitals
What is required for two electrons to occupy the same orbital?
They must have opposite spins - the Pauli Exclusion Principle
In electron configuration notation, what do the numbers refer to, what are they called, and what letter is used to represent them?
The numbers are called principal quantum numbers, they are represented by the letter n, and they refer to energy fields aka shells
Electrons in the outermost shells have ______ energy than those in the innermost shell.
Higher
Remember: The negatively charged electron is attracted to the positively charged proton. It takes more energy to send it further away from the proton.
How many sub-levels does each energy level have?
The same number as the principal quantum number. So energy level 1 has 1 sub-level, energy level 2 has 2 sub-levels, etc.
What formula is used to predict how many electrons can fit into a given shell/energy level?
2n2
What are the levels of electron configuration from broadest to narrowest?
- Energy level/shell
- Sub-level/sub-shell
- Orbital
How many orbitals is in each sublevel?
s = 1
p = 3
d = 5
f = 7
How many electrons can fit in each sublevel?
s - 2
p - 6
d - 10
f - 14
In which order are orbitals filled (up to 5d)
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d
What is the Pauli Exclusion Principle?
That two electrons occupying the same orbital must have opposite spin
In electron configuration, what do arrows pointing up or down indicate?
Electrons spinning in one or the other direction
Write the electron configuration of Bromine (z = 35) in both notation styles
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
[Ar] 4s2 3d10 4p5
How else are the different energy levels sometimes notated?
1 = K
2 = L
3 = M
4 = N
5 = O
6 = P
7 = Q
What are the orbitals in the p sublevel?
px, py, pz
Remember: The subscript refers to the axis the orbital aligns along
What is depicted here?
Hybridised orbitals - sp3
What is the Aufbau principle?
The principle that electrons fill lower energy fields before higher energy fields (and therefore determines how we determine electron configuration)
How much is the hybridised sp3 orbital influenced by s and p?
s - 25%
p - 75%
Remember: s-orbitals can hold 2 electrons and p orbitals can hold 6. The percentages match this. It’s also contained in the name (1s3p = sp3 orbital)
What is Hund’s rule?
Before a second electron can be placed in any orbital, all the orbitals of a sub-level must have at least one electron and all must have the same spin.
From electron configuration notation, how can you figure out how many valence electrons an element has?
These will be the electrons noted separately in noble gas notation.
e.g. Silicon = [Ne]3s23p2 = 4 valence electrons
What is the strongest form of covalent bond?
The σ (sigma) bond
What are orbitals with the same energy level called?
Degenerate orbitals
What are degenerate orbitals?
Orbitals with the same energy level
Which principle states that electrons fill lower energy fields before higher energy fields
Aufbau principle
Which principle states that before a second electron can be placed in any orbital, all the orbitals of a sub-level must have at least one electron and all must have the same spin.
Hund’s rule
What level of energy would we expect in sp2 orbitals?
About two thirds the energy of the p orbitals
Remember: It’s in the name. The three sp2 orbitals are hybrids of one s and two p orbitals, so they have 33% s character and 67% p character.
How many sigma and pi bonds are contained in this molecule?
7 sigma
2 pi
Remember: Every single bond is a sigma bond, every double bond is one sigma and one pi bond.
Which kind of orbitals make sigma bonds?
Hybridized orbitals
Which kind of orbitals make pi bonds?
Unhybridized orbitals
What kind of bonds can hybridized orbitals make?
Sigma bonds
What is this symbol?
σ
Sigma (lower case)
What kind of bonds are contained in single, double, and triple covalent bonds?
Single: one sigma
Double: one sigma and one pi
Triple: one sigma and two pi
Remember: it’s always only one sigma
Triple bonds are ______ but also _______ than single bonds.
Stronger, shorter
What’s the main difference between pi bonds and sigma bonds?
In pi bonds the orbitals overlap along parallel axes, in sigma bonds they overlap along the same axis
Which type of bond is stronger, pi or sigma?
Sigma
Why do single bonds allow for rotation but not double bonds?
Single bonds are sigma bonds - the overlap in orbitals is along the same axis so one side or another rotating doesn’t affect the overlap.
Double bonds have one pi bond. These involve parallel overlap, meaning if one side of the bond rotates, the overlap will be gone.
What determines which hybridization will occur in an atom?
The number of “groups” attached to the atom (the steric number). Groups are either bonds or lone pairs. Double and triple bonds are considered one group.
1 group = s
2 groups = sp
3 groups = sp2
4 groups = sp3
5 groups = dsp3
6 groups = d2sp3
What hybridization do we expect in the carbon atom of a methane molecule?
sp3
Remember: In methane (CH4) the carbon atom has four groups attached to it. Four groups means sp3
What characteristics do bonds with higher s character tend to have?
Stronger and shorter
How can you figure out whether one single bond is stronger or weaker than another?
Take the average s-character from their hybrid bonds.
Remember: Bonds with higher percentage of s-character tend to be shorter and stronger. Figure out the hybridisation of the two bonded atoms, then their percentage s-character, then average that percentage.
________ but not ______ electron pairs are counted as groups when determining hybridisation
Localised, delocalised
When do electron orbitals tend to hybridize?
When bonding
What difference in the electron configuration of carbon would we expect between a lone carbon atom, and a carbon in methane?
The lone carbon atom will follow the Aufbau Principle and be configured 1s22s22p2
However the carbon in the methane molecule will form bonds using hybrid orbitals (sp3)
In this case, instead of having two electrons of opposite spin in the 2s sub-level, and two of the same spin in different orbitals of the 2p sub-level, there will be one electron each (same spin) in four hybrid orbitals - like 1s22sp312sp312sp312sp31
What is the steric number?
The number of “groups” attached to the atom (sigma bonds and lone pairs) for the purpose of figuring out hybridization type
What effect on molecular geometry does a lone pair have?
It repels covalent bonds more than the bonds repel each other, so the bonds tend to be closer to each other and further from the lone pair.
Why are sp2 bonds shorter than sp3 bonds?
sp2 bonds have a higher s character than sp3 bonds. Since the electron is close to the nucleus in an s orbital, the sp2 orbital is also closer to the nucleus than the sp3 orbital, therefore sp2 bonds are shorter.
Identify this molecule shape
Linear
Identify this molecule shape
Tetrahedral, bent
Identify this molecule shape
Tetrahedral
Identify this molecule shape
Trigonal planar bent
Identify this molecule shape
Trigonal planar
Identify this molecule shape
Trigonal pyramidal
What is constitutional isomer another term for?
Structural isomer
What is the condensed structure for this molecule?
(CH3)2CHOH
Draw this as a lewis dot structure: (CH3)3COCH3
Remember: one carbon can be linked to multiple other carbons
Draw this molecule using a bond-line structure
How should carbons in chains be represented in a bond-line structure?
As a zig-zag
Create a 3D bond-line structure for this molecule
Remember: you can predict the shape based on the type of hybridized bond. For e.g. the central carbon will have sp2 orbitals, meaning the shape will be trigonal planar, therefore we know the oxygen will be on the same place as the carbons.
What does a dashed line on a bond-line structure indicate?
The bond points away from you in space
What does a solid wedge on a bond-line structure indicate?
The bond is pointing towards you in space
