Chemistry mid-year term Flashcards
What is matter?
Anything that has mass or volume
What is an element?
Pure form of matter-cannot be broken down.
What is a compound?
Combination of 2 or more atoms of different elements chemically combined in a fixed ratio.
What is a mixture?
2 or more substances mixed together, Not chemically combined.
What are pure substances?
A substance/matter made up of the same type of atom-contains a fixed ration.
What are diatomic elements?
2 atoms of the same element combined.
What is a solid?
State of matter that has a fixed shape/volume.
What is a liquid?
State of matter that has a fixed volume but no fixed shape.
What is a gas?
State of matter that has no fixed volume or fixed shape.
How can we predict the phase of a substance at a given temperature?
Looking at its Boiling/Melting point
What is a chemical formula?
Indicates the elements and their properties in a compound.
How do we indicate the phase of matter in a chemical formula?
By putting a subscript of (s), (L), (G) to represent its phase.
What do the coefficients and subscripts represent in a chemical formula?
The coefficient represent how many molecules there are. The subscript represents how much of each elements there are.
What is a physical properties?
A property that can change without changing the chemical composition.
What is a chemical properties?
A property that can only be changed by changing the chemical composition.
What is a physical change?
A change that does not affect the chemical composition.
What is a chemical change?
A change that changes the chemical composition.
Filtration
Based on particle size. Separates undissolved solid/liquids.
Magnetism
Separates metals in a mixture base on magnetic activity.
Distillation
Separates liquids based on boiling points.
Crystallization
Liquid evaporates and solids crystallize. Separating solids/liquids.
Chromatography
Base on solbility.
Decantation
Pour the liquid out.
What is the general format for scientific notations?
X.Y x 10Z
X.Y-Coefficient
10- Base
Z- Exponent
How do we convert a number to scientific notation?
Step 1: Move the decimal, or place a decimal, to create a number between 1 and 10. This will be the coefficient.
Step 2: Count the number of places you moved the decimal. This will be the exponent. If you moved the decimal to the right, the exponent will be negative. If you moved it to the left, the exponent will be positive.
Step 3: Write out the coefficient from step 1 multiplied by 10 raised to the exponent from step 2.
How can we convert a scientific notation to a number?
1)Move the decimal point to the right for positive exponents of 10. The exponent tells you how many places to move.
2)Move the decimal point to the left for negative exponents of 10. Again, the exponent tells you how many places to move.
What are the rules for adding, subtracting, multiplying and dividing any numbers in scientific notation?
Multiplying: Add the exponents
Divide: Subtract the exponents
Add/Subtract: Make the exponents the same, then add/subtract.
What are the steps for dimensional analysis?
1)Determine conversion factor
2)Start with what is given
3)Multiply given with conversion factor so that the units cancel out.
What are significant figures?
All know digits in a measurement plus one estimated digit.
What are the rules for counting significant figures?
Multi/divide-Answer should have the least amount of sig-fig when solved out
Add/Sub- Anser should have the least amount of sig-fig when solved.
(we count as soon as we hit the decimal, left or right)
What is precision in measurements?
How close the measurements are to each other.
How do we calculate accuracy?
Percent error (absolute value)
What is accuracy in measurements?
How close the measurements are to the actual value.
Define density
Amount of substance in a given amount os space.
How can we calculate density?
D=M/V
How can we calculate volume?
V= M/D
How can we calculate mass?
M= D x V
What is a mole?
Unit to count the number of atoms/molecules.
How can we convert between moles and mass?
Find the GFM of 1 molecule and multiply it with the number of moles.
How can we convert between moles and # of particles/atoms/molecules?
(1 mole = 6.02 x 10^23) x Number of mole
What is Avogadro’s constant?
1 mole of anything = 6.02 x 10^23
John Dalton atomic model
All matter is made of tiny particles called atoms. Atoms are indivisible- Law of conservation
Model: Atom is a solid sphere
J.J. Thomson atomic model
Used the cathode ray tube experiment to say atoms contain small negative charged particles.
Model: Plum pudding model.
Ernest Rutherford atomic model
Used the gold foil experiment to conclude that atoms have a dense positive central core called a nucleus and the rest is empty space. Some particles deflected from the gold foil.
Model: A sphere in the middle of the atom containing positive charged molecules surrounded by negatively charged molecules. (atom still a ball)
Bohr atomic model
Commonly used model, came to the conclusion that electrons revolved in orbits/shell. Each orbit has a different number of electrons/energy.
Schrodinger atomic model
Most accurate model, concluded that electron revolved in orbitals- Area where it is most likely to form an electron- electron cloud/wave model.
What are subatomic particles and where are they located?
Protons, Neutrons, Electrons.
Protons- Nucleus
Neutrons- Nucleus
Electrons- Outside molecule.
How can we determine the number of each subatomic particle in an atom?
Protons- Atomic number
Electrons- Amount of proton/ Atomic number.
Neutrons- Mass- Atomic number
How to determine the atomic and nuclear charge?
Atomic charge- Number of Protons (minus) Number of Electrons
Nuclear charge- Depends on the # of protons. Ex 4p- +4
What is a neutral atom?
A neutral atom is when the number of protons equal the number of electrons.
What is a cation?
Cation- When an atom has less electron, its a positive ion.
What is a anion?
Anion- When an atom has more electrons, its a negative ion.
What are isotopes?
Atoms of the same element that have the same atomic number but different mass number.
How can we calculate the % abundance of each isotope?
(How much the isotope occurs in a sample/ total sample) x 100.
What does the average atomic mass of an element tell us about the % abundance of the different isotopes of that element?
It tells you how likely it is to occur in nature.
What is isotope notation?
A way to write the element, mass, and number of protons in atom. Mass at top- Element in the middle- Number of protons at the bottom.
What is ground state electron configuration?
Arrangement of electrons in each orbit of an atom.
What does electron configuration tell us?
It tells us where the electrons are located in around the nucleus. Tells us the energy levels of each orbit/shell/
What are principal energy levels?
Orbits/Shell(n)
Why are orbits called energy levels?
Each orbit contains a different amount of energy due to different amount of electrons.
What is a valence shell and what are valence electrons?
Valence shells- Outer most shell of the atom.
Valence electrons- Electrons located on the valence shells.
How do you determine the number of valence electrons?
Look at your reference sheet
Electrons in each orbit: 2(n)^2
Why and how do atoms make ions?
Atoms want to become stable and have 8 electrons in their outer most shell (octet rule). An atom can make an ion by gaining or losing an electron. (Electronegativity/Ionization energy)
What is an excited state?
High energy state when electrons absorbs energy and move to a higher orbit.
How is a bright line spectrum produced?
Produced when electrons move from excited state to ground state and emit different amounts of energy at different wavelengths.
How can we identify an unknown using the bright line spectrum?
Different light is emitted for each element.
How was Mendeleev’s periodic table organized?
Increasing weight
Periods
Rows in the periodic table with all the elements that have the same number of orbits.
Group
Column with all elements that have the same numer of valence electrons.
What is Periodicity
if elements are arranged in an order, the properties of elements would repeat after some period.
Metalloids
Properties similar to metal and non-metals, Elements around the staircase except Al and Po
Different groups categorization
Group 1- Alkaline metals
Group 2- Alkaline earth metals
Group 3-12- Transition metals
Group 17- Halogens
Group 18- Noble gases
Ions of which group(s) have the tendency to form colored solutions?
Group 3-12- Transition metals
What is atomic radius
Distance between the nucleus and the valence electrons.
Are cations smaller / bigger than the atom? Why?
Smaller, loses an orbit/energy level
Are anions smaller / bigger than the atom? Why?
Bigger, gain an orbital/energy level
What’s the trend for atomic radius down the group and across the period in the periodic table?
Increase as you go down, decrease as you go across the period.
What’s the trend for ionization energy down the group and across the period in the periodic table?
Decrease as you go down, increase as you go across.
What’s the trend for electronegativity down the group and across the period in the periodic table?
Decreases as you go down, increase as you go across.
What’s the trend for metallic character down the group and across the period in the periodic table?
Increases as you go down, decreases as you go across.
How are ionic bonds formed?
by the complete transfer of some electrons from one atom to another- between metals and non-metals.
What is a polyatomic ion?
Ion that has more than 1 atoms
How can we define electricity?
Movemt of charged particles
What do we know about the electrical conductivity of ionic compounds?
good conductors of electricity in solutions only.
What are metallic bonds?
Attraction between 2 metals- positively charged metal ion held together by a sea of electrons
How are covalent bonds formed?
Attraction between 2 non-metals as they share their electrons.
