Chemistry Unit 2

How to find the number of protons, neutrons, electrons from a nuclear symbol

Protons - look at the periodic table, for the atomic number (number of protons in a nucleus)

Neutrons - they give a mass number, specific for one isotope, and then subtract protons from mass number

Electrons - if there is an ion, eg 2+/-, then add or subtract to the number of protons, if not equal to number of protons. 2+, is two extra protons, 2- is two extra electrons

Relative atomic mass

The average mass relative to all isotopes present and their abundance

Mass number

the specific mass number for that specific isotope, given to find neutrons

What determines the different chemical properties of atoms?

number of protons, and electrons

What are isotopes?

same number of protons different number of neutrons

what produces emission spectra

produced by atoms emitting photons when electrons excited states return to lower energy levels

describe the relationship between wavelength and the emission spectrum

towards the red end there is less energy, thus the wavelengths will be longer, than compared to the violet side.

describe the relationship between frequency and the emission spectrum

towards the red end there is less energy, longer wavelengths, the lower the frequency

whats the difference between continuous and line spectrum, when do lines convergew in line spec

A continuous spectrum contains all wavelengths of light in a certain range. Where a spectral line is a spectrum in which light of only a certain wavelength is emitted or absorbed,

lines converge at high frequency

How to describe the emission spectrum of hydrogen

When a hydrogen atom is excited, its electron moves to a higher energy level. As the electron returns to lower energy levels, it emits photons with energies specific to the energy level transitions. These emitted photons correspond to specific wavelengths, which appear as distinct colored lines in the spectrum.

What does the energy transition to N=2, N=1, N=3 mean

visible light, ultra violet light, infra red radiation

What quantitive and qualitative data can be collected from instruments, eg, prims

quantitive; wavelengths of light from the coloured lines, frequency of emission lines

qualitative; observe and describe the colours, line spectra, showing the characteristics of a gas

How does absorption spectra show existence of different elements

since the absoprtion spectrum is a finger print for elements, it allows for scientist to identify the specific elements, thus if examining and discovering lines that do not match already found elements, it is prove for a new one

What are the max number of electrons for every energy level

2n², where n is is the energy level

how to find the total number of orbitals at an energy level

n², where n is is the energy level

How does an element's highest main energy level relate to it's period number on the periodic table

since there are 7 energy levels, and thus seven periods, thus the period it is in determines the energy level

What does the shape for the s orbital look like

A circle over the three axles

What does the shape for the three p orbitals look like, px, py, pz

a propellor based off of the axis, x is horizontal, y is diagonal, and z is vertical

What is the relationship between energy sublevels and the block nature on the periodic table

the first two groups are the s level, max of 2 electrons

groups 13- 18 is the p level, max 6 electrons

groups 3- 12 is the d level, max 10 electrons

How to make the electron configuration with the sublevels

order is s-p-d-f, the number before the orbital shows the energy level, found in periodic table which period they are in (vertical). So an element would first fill up the first energy level 1s, then the second energy level, 2s and 2p, then the third 3s 3p and 3d, then the fourth 4s, 4p, 4d, and 4f.

the number after the energy and sublevel shows the number of electrons on the level

If there is a noble gas first, we can write its symbol instead of the configuration.

What are the exceptions to the electron configuration, and what are their configuration

Cr and Cu, chromium and copper, (Ar) 4s1 3d5 and (Ar) 4s1 3d10

why are there two exceptions to electron configuration

since electrons repel each other, and therefore appear where there is more space,

How has the organisation of elements in the periodic table help discover new elements

the periodic table is based off of properties, when first made there were many gaps in between elements, from this scientist were able to deduct that another element with the same properties and a mass that would correspond with the other group will occur.

Found out through the emission spectrum

Periodicty of atomic radius and how to calculate it

decreases as you move from left to right across a period, increase in nuclear charge more protons, and they increase when gong down a group since there is an increase in electron shells

calculated by measuring the distance between the nuclei of two touching atoms, and then halving that distance.

Periodicty of ionic radius and how to calculate it

will increase when you go down periods, since there is an increase in electron shells. they will decrease moving along the period, since there is a higher effective nuclear charge pulling the electrons closer to the nucleus, pulling them closer results in a smaller ionic nucleus

calculated by the distance between the two nuclei and dividing it according to the atomic sizes

What is ionization energy

the energy required to remove an electron from an atom

Periodicty of ionization energy

will increase from left to right since the stability of the valence electron increases, more electrons present, thus less shielding effect and more attraction to the nucleus, thus more energy to remove

will decrease when going down a group since there is more shielding effect, since there are more energy levels and thus less attraction of the electrons to the nucleus

What is electron affinity

the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous -1 ions

Periodicty of electron affinity

increase across a table, stronger attraction between the nucleus and electrons since there is less shielding effect, thus more energy released

decreases when going down a group since there are more energy shells thus less attraction and more shielding effect, less energy released.

What is electronegativity

ability of an atom to attract electrons

Periodicty of electronegativity

will increase going across a period since there is less shielding effect causing more attraction towards the nucleus due to an increase in protons more likely to gain than lose an electron

will decrease going down a group since there is more energy levels, more shielding effect, and therefore less of an attraction towards the nucleus, therefore more likely to lose an electron than gain it.

oxidation states of an atom in an ion (electronegativty)

group 1 +1 (s block)

group 2 +2 (s block)

group 3-12 (d block) +2 or +3

group 13 +3

group 14 +4

group 15 -3

etc

what is an anion and what is a cation

Anion: negatively charged ion

Cation: positively charged ion

What is Zeff

effective nuclear charge

what is a Molecular covalent bond and properties

Electrostatic attraction between 2 positive nuclei and the shared electron pairs between them.

what is an ionic bond and properties

Electrostatic attraction between oppositely charged ions.

very soluble

hard and brittle

non directional

and electrically conductive - from free moving ions

how to name ionic bonds

cation first then anion AlF₃ aluminum fluoride

polar vs non polar covalent bonds

A small electronegativity difference (Delta EN) between two bonding elements results in nonpolar covalent bonding, where electron pairs are shared more or less evenly.

Larger electronegativity differences between two bonding elements results in polar covalent bonding, where electron pairs are shared unevely between two atoms. This results in uneven electron distribution as well as partial charges at either end of the bond.

Metallic bond and properties

Electrostatic attraction between a lattice of positive metal cations and the delocalized valence electrons moving between them.

nondirectional - from delocalised electrons

high thermal and electrical conductivity - from delocalised electrons and Thermal from closely packed ions to transfer energy

highly luster - electrons reflect visible light

highly malleable because of sliding

Giant Covalent structure and properties and examples

-Crystalline lattice, where all the atoms are bonded together by covalent bonds

-The pattern of the atoms is regular and repeating throughout the structure

Carbon (Diamond), Sillicon, and Sillicon Diozide

not electriclaly conductive

not soluable

very hard and brittle

hardness

This depends on the strength of the attraction between neighboring particles. Stronger interparticle attractions lead to solids that are harder, and in many cases, more brittle, meaning they tend to break/split apart rather than bend. Weak interparticle attractions can lead to substances being softer solids. If attractions are weak enough than substances will be liquid or gas, and so the term "hardness" would not apply. Malleability, the ability to be shaped, could also be linked to hardness, and is a unique property of metals,

electrical conductivity

The ability to conduct electricity requires the presence of freemoving charges, so that current (a flow of electrons) can occur in a circuit.

thermal conductivity

The ability to conduct heat is based on how efficiently atoms can pass along thermal energy to one another. Atoms that are more tightly packed together tend to be better conductors of thermal energy, while molecular substances, especially gases, tend to do so less efficiently.

solubility

Polar substances (those with partial charges) tend to mix well and form attractions with other particles that are also polar. Nonpolar substances, on the other hand, do not mix well with polar substances, and instead mix better with other nonpolar substances.

bond enthalpies

The energy required to break (1 mole of) a bond in the gas phase.

Allotropes of Carbon

Diamond

Graphite

Graphene

Bucky Ball

Bucky Ball

distorted trigonal planar,

each carbon atom is covalently bonded to 3 other carbon atoms

delocalised electrons aorund the ball, but poor electrical conductor as e cant move between balls

por thermal conductor

soluble in nonpolar solvents

very light and strong

Graphene

each carbon atom covalently bonded to 3 other

trigonal planar

single layer, delocalised electrons around

strong electrical and thermal conductors

strong

graphite

carbon atom covalently bonded to 3

trigonal planar

london forces in between graphene layers

pi electrons delocalised across the layers

high electrical conductors poor thermal conductors

very brittle and soft

Diamond

carbon atom bonded to 4 carbon atoms

tertahedral

electrons localised

not electrical conductive no delcoalised electrons

hardest substance very brittle, high melting point

VSEPR Theory

In the Valence Shell, electron pairs will repel each other as far as possible.

While the electron pairs are stuck between the positive nuclei, they push each other as far as possible around the central atom.

chromatography

Chromatography is a technique that takes involves separating components of mixtures, mainly for identification purposes.

All chromatography involves a stationary phase, which is a substance/structure that does not move, and a mobile phase, which is a substance/mixture that moves along the stationary phase.

Depending on the interactions between the components of the mixture and these different phases, the different components of the mixture move along with the mobile phase to different degrees. This causes the components to separate out, which allows them to be identified.

Resonance

Resonance occurs when there is more than one possible location for a pi-bond.

The delocalized pi electrons create a more stable hybrid structure

that length is in between the length of a single and double bond

Bond order

A way of describing the actual, net number of bonds between to atoms. This includes the partial bonds that exist as a result of electron delocalization.

#bonds between resonance atoms

#bonds resonance bond locations

how to determine the formal charge

smaller formal charge is favoured

1) Each atom "owns" all of its non-bonding electrons

2) Each atom "owns" 1 electron out of each bonding pair.

*All covalent bonds are assumed to be 100% covalent.

In other words: *Electronegativity is ignored**

3) Compare the # of valence electrons the atom has normally to the number it "owns" in the molecule or ion.

4)The sum of all the formal charges in a species must add up to the total charge on that species.

F.C. = (# valence e-) - (# non-bonding e-) - (1/2 bonding e-)

expanded octets

where atoms obtain more than a full valence shell of 8 electrons.

electron energy levels converge at higher energies and beginning in the third energy level there are d-orbitals for the first time. As a result, elements from the 3p-block can use otherwise empty 3d-orbitals to share more than 8 electrons.

hybradization

every atom can have a hybradized state

electron gets promoted from 2s to 2p making sp3, this allows for less electron repulsion

Linear - sp

Trigonal planar - sp2

Tetrahedral - sp3

sigma

A sigma (σ) bond forms when two atomic orbitals overlap head on. This results in symmetry around the bond axis and electron density between the two bonding nuclei.

All single covalent bonds are sigma bonds. In addition, one of the bonds of any double or triple bond is also a sigma bond.

pi bonds

A pi bond forms from the sideways overlap of parallel p-orbitals and results in electron density above AND below the bond axis for each pi-bond.

In double and triple bonds, however, the extra bond(s) are created differently. The shared electron pairs cannot occupy the same space as the first sigma bond. As a result, they form through pi bonds.

coordination bond

covalent bond where both electrons of the shared pair originate from same atom

London forces

a temporary attractive force due to the formation of temporary dipoles in a nonpolar molecule.

greater surface area increases london forces

Heavier atoms or molecules have more electrons, and stronger London forces.

dipole dipole forces

attractive forces between the positive end of one polar molecule and the negative end of another polar molecule.

hydrogen bonding

A hydrogen bond is the intermolecular force between the nonbonding electron pair of a fluorine, oxygen or nitrogen atom and the hydrogen atom from a neighboring molecule that is covalently bonded to a fluorine, oxygen or nitrogen atom.

occur between molecules or within

what influences the heat produced in a reaction

the higher concentration produces a higher temp