Unit 1 half test Flashcards
How the history of an atom evolved
1) Greek democritus had the idea for an atom: NO protons No electrons, No neutrons
2) John Dalton: Billiard balls no P no E no N
3) J.J thomson: Plum pudding model. Random negative spots everythign was positive.
4) Ruthorford: Centre was positive (neucleus) with elections
4.5/5) Bhor: Same thing with energy levels (shells)
6) Chadwick: added neutrons
7) Schrodinger: electron cloud
What is the law of constant composition
Compounds always have the same percentage composition by mass. (Same formula)
What are isotopes
Two atoms are isotopes if they have the same number of protons, but they have different numbers of neutrons.
This means that:
Isotopes are atoms of the same element.
Isotopes have different atomic masses.
Isotopes have different number of neutrons in their nuclei.
In the average atomic mass equation
(AAM (u) = (% ab1 x mass1) + (% ab2 x mass2) +… )
What does AAM mean, %ab mean, and mass mean.
AAM = Average Atomic Mass
%ab1 = Percent abundance of isotope
mass1 = Mass of isotope
What is periodic law
When elements are arranged in order of increasing atomic number, there is a regular pattern in their chemical and physical properties – i.e. periodic trends
What do elements in the same group share
the same outer orbital configuration in consecutively higher energy levels
What do elements in the same period share
outer electrons in the same energy level
What is atomic radius, what factors affect it, and what is the trend
The distance between the nucleus and the valence electrons
1)Number of shells
2)Strengths of attractions felt by the valence electrons toward the nucleus (Nuclear Charge)(Zeff)
3)Shielding effect
The trend:
arrow pointing bottom left
What is the Nuclear charge
of electrons also increases, but inner layers are still the same 🡪 nuclear (proton) pull is stronger
Ignore that its glitched^
.
A measure of the stregth of a nucles’ pull as we move across a period the number of protons increases in nuclear charge.
This affects periodic trends
What is the sheilding effect
electrons in innermost shells “block” or shield the outermost electrons from the nucleus’ attractive force.
This mainly effects group trends.
Trends in ionic radius
Positive ions are smaller than the neutral atoms from which they are formed
Electrons are lost from energy levels farthest from the nucleus
Fewer electrons but same “+” pull from nucleus 🡪Remaining electrons pulled closer to the nucleus
Negative ions are larger than the neutral atoms from which they are formed
Electrons are gained, resulting in smaller effective nuclear charge for the greater number of electrons
Repulsive forces between electrons increases across the periods
What is ionization energy, what factors affect it, and what is the trend
The amount of energy required to remove an electron from an atom or ion in the gaseous state. Outer electrons are easier to remove
1)Strengths of attractions felt by the valence electrons toward the nucleus (Nuclear Charge)(Zeff)
2)Shielding effect
arrow pointing top right
What is electron affinity
Electron Affinity – A measure of the energy lost or gained when an electron is added to an uncharged atom.
The lower the number, the greater the electron affinity.
Greater E.A. means that energy is actually released when an electron is added. Therefore, the value is expressed as a negative. Units for both i.e. and e.a. are KJ/mol.
Eg. X + 1e- = X- + energy
The greater the attraction between an atom and an added electron the more energy that will be released.
Arrow pointing top right
What is electronegativity
Electronegativity is a measure of an atom’s ability to attract shared electrons to itself.
You have the trend for this on your periodic table.
Arrow pointing top right
What does isoelectronic or the octet rule mean
“Atoms tend to bond in such a way that will allow them to have 8 electrons in their valence shells.”
(Hydrogen and Helium are obvious exceptions since they only need 2 electrons to fill their outer shell)
What type of bond forms large crystal lattice structures
Ionic compounds (and some covalent compounds like diamond)
What is a combining capacity
The combining capacity is the number of covalent bonds that a non-metal atom will usually make to form a stable molecule.
Recall the ball & peg molecules that you made earlier. The number of holes in each type of atom represents its combining capacity.
what is ammonia
NH3
What are the tresholds for ionic, polar, and nonpolar bonds.
ΔEN > 1.7, Then the bond is ionic.
1.7 - 0.5 , Then the bond is polar covalent.
0.1 - 0.4, Then the bond is non polar 0, then the bond is pure covalent.
What molecular shape does 2 total, 2 bonds and 0 lone pairs have
linear 180*
What molecular shape does 3 total, 2 bonds and 1 lone pairs have
Bent 120*
What molecular shape does 3 total, 3 bonds and 0 lone pairs have
trigonal planar
120*
What molecular shape does 4 total, 4 bonds and 0 lone pairs have
tetrahedral 109.5*
(triangle based piramid)
What molecular shape does 4 total, 3 bonds and 1 lone pairs have
Trigonal pyramidal 107*
(triangle based piramid with no top)
What molecular shape does 4 total, 2 bonds and 2 lone pairs have
bent 104.5*
water
when is a molecule polar
A molecule is said to be polar if it contains polar covalent bonds AND its shape is “asymmetrical”
What are london dispersion forces or Van der Waals’ forces
This force of attraction is caused by the random creation of temporary dipoles within molecules known as “instantaneous dipole moments”.
Consider that electrons are always in motion. Thus, even in a non-polar molecule there will be instances when the movement of electrons results in partially positive and partially negative regions which attract neighbouring molecules. This occurs randomly, but frequently.
The strength of dispersion forces increases as the molecular mass of the molecule increases due to an increase in the number of electrons allowing for the creation of stronger instantaneous dipoles. Thus, large molecules often have higher boiling points.
What are dipole-dipole attractions
Electrostatic attraction which occurs between molecules with permanent dipoles, ie. polar molecules.
This permanent dipole means that the molecules ‘stick’ together
this means they require energy to pull apart ergo a higher m.p/b.p
tend not to be gasses at room temperature
Eg. HCl
What is hydrogen bonding
Electrostatic attraction which occurs between molecules with permanent dipoles, ie. polar molecules.
This permanent dipole means that the molecules ‘stick’ together
this means they require energy to pull apart ergo a higher m.p/b.p
tend not to be gasses at room temperature
fluorine, oxygen, or nitrogen.
what is an intramolecular force
Recall that intramolecular forces hold atoms together within a molecule. Such bonds determine the chemical properties of a compound such as reactivity.
(One molecule)
what are intermolecular forces
Intermolecular forces exist between molecules, and influence physical properties.
(many molecules)
