General Chemistry 1 Flashcards
What is accuracy?
A measurement giving the Actual value for a sample with a limited deviation
What is precision?
The repeatability of a set of measurements on the same sample
Why is glass preferred in labs?
Inert, strength, transparency, heat resistant
What are examples of calibrated glassware?
Graduated cylinder, graduated pipet, volumetric pipet , volumetric flask
What does the shape of the meniscus tell you?
Meniscus is convex when the molecules of liquid are attracted to each other. Meniscus is concave when the liquid is attracted to the sides of the cylinder
What is a pH meter?
Made of glass probe and electronic meter, uses difference in voltage to calculate PH, sample must be at known temperature
How is litmus paper used?
Can be used to determine pH, paper is red under acidic conditions, paper is blue under basic conditions, paper is purple at neutral pH
What are the two types of laboratory balances?
Standard laboratory balances and analytical balances (with sliding doors)
What is calorimetry?
Way for chemist to measure energy content of a substance
What are atoms composed of?
Subatomic particles; protons neutrons and electrons
What are isotopes?
Atoms of the same element with different masses due to a different number of neutrons
What are key points from Dalton’s hypothesis?
- All elements are made of very small particles called atoms (atoms of a given element are identical in size, mass and chemical properties)
- All compounds are composed of atoms of more than one element
- Chemical reactions involve only the separation, combination, or rearrangement of atoms, it does NOT result in the creation or destruction of atoms
What is atomic number and what is atomic mass number?
Atomic mass number is total amount of protons and neutrons. Atomic number is total number of protons
E=hf
E= energy value of a quantum h= Planck constant (6.626 x10^34 j .s) f = frequency of radiation
L = NH/2 π
N= principal quantum number H= Planck constant L = angular momentum of an electron
E=hc/λ
λ = wavelength of radiation
C= 3x 10^ 8 m/s
h=Planck constant
E= energy of electron
What is an orbital?
A representation of the probability of finding an electron within a given region
What is the Heisenberg uncertainty principle?
States that it is impossible to simultaneously determine an accurate momentum and the position of an electron
What is the pauli exclusion principle?
No two electrons in a given atom can have the same set of 4 quantum numbers
How do you calculate the maximum number of electrons in an electron shell?
2n^2
What is the azimuthal/second quantum number?
Designated by the letter l, tells us shape of the orbitals and refers to the sub shells or sub levels that occur within each principal energy level, can range from 0 to n-1
What sub shells do L= 0, 1, 2, 3 mean?
S, p, d and f subshells respectively
How do you calculate the maximum number of electrons that can exist within a sub shell?
4L+2
What is the magnetic/ third quantum number?
Designated with ml, this number describes the orientation of the orbital in space, possible values range from l to -l including 0
What is the fourth/spin quantum number?
Denoted by ms, has 2 spin orientations either 1/2 or -1/2
What is Aufbau’s Principle?
Subshells are filled from lowest to highest energy and each subshell will fill completely before electrons begin to enter the next one
What is Hund’s Rule?
In subshells that contain more than one orbital, orbitals are filled such that there is a maximum number of half filled orbitals with parallel spins
What does paramagnetic and diamagnetic refer to?
- If a material has unpaired electron, a magnetic field will align the spins of these electrons and weakly attract the atom to the field, and these materials are said to be paramagnetic
- Materials that have no unpaired electrons and are slightly repelled by a magnetic field are said to be diamagnetic
What is periodic law?
The chemical properties of the elements are dependent in systemic way upon their atomic numbers
What are A and B elements?
- The A elements are the representative elements which have either s or p sublevels as their outermost orbitals
- The B elements are the non representative elements including the transition elements and lanthanide and actinide series , which have partly filled d or f sublevels
What is effective nuclear charge (Zeff)?
The net positive charge from the nucleus, as felt by an electron
What are the periodic trends for Zeff?
Down a given column the outermost electrons become less tightly bound to the nucleus because the number of filled principal energy levels (which shield the outermost electrons from attraction by the nucleus) increases downward within each group
THEREFORE Zeff is at a max at the top right of the periodic table
What are the periodic trends for atomic radii?
Atomic radius decreases across a period from left to right and increases down a given group
From left to right across a period as electrons are added to the outer energy shell, the electrons get pulled closer to nuclear because Zeff increases as well
What are the trends for ionic radius for cations and anions?
- Usually cations (positive ions) will be smaller than the corresponding neutral atoms because they have fewer electrons and less repulsion among the remaining electrons
- Anions (negative ions) will be larger because more number of electrons and more repulsion
What is ionization energy?
- The energy required to completely remove an electron from a gaseous atom or ion
- The first ionization energy is the energy required to remove one valence electron and then the second ionization energy is the energy needed to remove a second valence electron
- Usually the second ionization energy is greater than the first unless the removal of the second electron would give it a fully filled or half filled valence shell
What are the periodic trends for ionization energy?
- Ionization energy increases from left to right across a period as Zeff increases
- Moving down a group, the ionization energy decreases as Zeff decreases
What is electron affinity and what are their trends?
- The energy change that occurs when an electron is added to a gaseous atom and it represents the ease in which the atom can accept an electron
- The higher the Zeff, the greater the electron affinity will be
- Positive electron affinity represents energy release when an electron is added to an atom OR negative electron affinity represents a release of energy ( FIRST USED MORE TIMES/COMMON)
- Group 2 (alkaline earth metals) have low electron affinity values because elements are relatively stable and s subshell is full
- Group 7 halogens have high electron affinities because the addition of an electron results in a completely filled shell
- Group 8 (noble gases) have electron affinities that are close to 0 because have full shells and cannot readily accept electrons
What is electronegativity?
A measure of the attraction an atom has for electrons in a chemical bond, the greater the atoms electronegativity the greater its attraction for bonding electrons
What is the periodic trend for electronegativity?
- Elements with low Zeff will have low electronegativities because their nuclei do not attract electrons strongly, while elements with a high Zeff wil have high electronegativity because of the strong pull the nucleus has on electrons
- Electronegativity increases from left to right across periods and decreases from top to bottom down a group
What are the types of elements?
Metals, nonmetals and metalloids
What are some properties of metals?
- Usually shiny solids, usually have high melting points and densities
- Can be deformed without breaking
- Malleable (can be hammered into shapes)
- Ductile (able to be drawn into wires)
- Good conductors of heat and electricity (few valence electrons)
- Large atomic radius, low ionization energy and low electronegativity
What are some properties of nonmetals?
- Poor conductors of heat and electricity
- High ionization energies and electronegativities
What are some properties of metalloids?
- Densities, boiling points and melting points fluctuate
- Have characteristics of both metals and nonmetals since they lie in the middle
- Boron, silicon, germanium,. Arsenic, antimony, and tellurium are metalloids
What is a cation and what is an anion?
Cation is a positive ion and anion is a negative ion
What are the Alkali Metals and what are their properties?
- Elements of Group 1
- Physical properties common to metals but their densities lower than metals
- Have largest atomic radius
- Metallic properties and high reactivity due to their low ionization energies, easily lose their valence electron
- Low electronegativities and react readily with non metals
What are the Alkaline Earth Metals and what are their properties?
- Elements of group 2
- Commonly form +2 cations
- Have low electronegativities and positive electron affinities
What are some properties of the carbon group?
- Family containing carbon, group 4, has non metals, metals and -metalloids
- All have 2 electrons in their outermost p subshells
- Participates in electron sharing, tends not to form ions
- Usually most stable with 4 covalent bonds
What is the pnictogens and what are their properties?
- Nitrogen and the elements below it in group 5
- Often form 3 covalent bonds per atom
- Nitrogen usually has a positive charge in organic reactions