Chemistry Midterm
Lewis Structure Rules
1. Draw a Lewis structure for each individual atom and determine the total number of valence electrons in the compound. 2. Arrange the Lewis structure to show how the atoms bond in the molecule 3. Distribute the dots so that each atom satisfies the octet rule.* 4. Change each pair of dots that represents a shared pair of electrons to a long dash. 5. Verify the structure by counting the number of electrons surrounding each atom
346 mL X 200 K / 546.4 K
100 mL
How many millimeters are there in 2.0 meters?
2000 mm
37.26 + 2.7 + 0.0015
40.0
How many grams are there in 5.0 kilograms
5000 g
Significant #? 4001.006 g
7
An atom in which one end has a partial positive charge and one end has a partial negative charge is called
A Dipole
When the forces between two hydrogen atoms balances, the atoms form?
A bond
If the difference in electronegativity is between 0 and 0.5, the bond is probably
A nonpolar covalent
Quantum number
A number that specifies the properties of electrons in an atom
What are the differences between physical and chemical properties?
A physical property is a property that can be determined without changing the nature of the substance, such as color, texture, density, solubility and melting and boiling points while chemical can only be determined by causing a chemical change.
If the difference in electronegativity is between 0.5 and 2.1, the bond is considered
A polar covalent
Define compound
A pure substance were atoms are bonded together
Orbital
A region in an atom where there is a high probability of finding electrons
Alpha particle
A small, positively charged particle which Rutherford directed at thin gold foil
Excited state
A state in which an atom has more energy than it does at its ground state
Changes in chemicals, or chemical reactions, take place [only in test tubes/all around us]
All around us
Dalton's atomic theory 1
All matter is composed of extremely small particles called atoms which cannot be subdivided, created, or destroyed
Electromagnetic spectrum
All of the frequencies r wavelengths of electromagnetic radiation
Specific heat?
Amount of heat required to raise the temperature of 1 g of something by 1 k
Nucleus
An atoms central region made up of protons and neutrons
Because of this constant change, bond length is always..
An average
Variable
Any aspect of an experiment that be changed to affect the outcome of the experiment
How does an atom differ from an element?
Atoms are the smallest unit of which elements are made
Dalton's atomic theory 2
Atoms of a given element are identical in their physical and chemical properties
Isotope
Atoms of an element that have different numbers of neutrons are called isotopes
Dalton's atomic theory 4
Atoms of different elements combine in simple, whole # ratios to form compounds
Dalton's atomic theory 3
Atoms of different elements differ in their physical and chemical properties
Symbol for gold
Au
Why did Thomson believe the Rays were particles?
Because a paddle when was set in motion by the ray
Why does a compound have characteristic properties?
Because every molecule of a compound is made up of the same numbers and kinds of atoms arranged in the same way.
Why is density a derived unit?
Because its value is obtained from two of the basic units, mass and volume
Why is a mole used to count atoms
Because working with big numbers is hard
The energy required to break a bond between two atoms is the
Bond energy
Chemical changes sometimes produce a gas, which you can detect by observing [bubbles/a precipitate] or by a change in [color/odor]
Bubbles; odor
Symbol for carbon
C
Physical change
Change in matter from one form to another without a change in chemical property
In a [physical/chemical] change, the identities of substance change and new substances form.
Chemical
Is milk souring physical or chemical?
Chemical
When two clear solutions mix and a precipitate forms, the mixture becomes [cloudy/clear]
Cloudy
The electronegativity of the atoms involved determines the type of
Covalent bond
When two atoms share electrons, they form a
Covalent bond
Chemical reactions may also absorb energy, which is indicated by a [increase/decrease] in temperature
Decrease
A chemical is any substance that has [definite/indefinite] composition
Definite
The simplest covalent bonds occur within what?
Diatomic molecules
Define mixture
Different component atoms that are not chemically bonded
How do wavelengths provide info about electron energy levels
Electrons release energy to move to Lower energy levels. This is released as light that has a specific wavelength
The capacity to do work is ____
Energy
Endothermic
Energy is absorbed
Exothermic
Energy is released
Heat?
Energy is transferred between objects that are at different temperatures.
Accuracy?
Extent to which a measurement approaches the value of quantity
Precision
Extent to which a series of measurements of the same quantity made in the way agree with one another
Liquids have a [fixed/variable] shape
Fixed
The characteristics of a solid include [fixed/variable] volume and shape.
Fixed
Bohr's model of an atom
Gave equations of space
Which groups compose the main-group elements?
Groups 1, 2, 13, 14, 15, 16, 17, 18
Dalton's atomic theory 5
In chemical reactions, atoms are combined, separated, or rearranged but are never created, destroyed, or changed.
When energy is released during a chemical reaction, temperature [increases/decreases]
Increases
Angular momentum quantum number
Indicates shape of the orbital
Principal quantum number
Indicates the main energy level occupied by an electron
Spin quantum number
Indicates the orientation of an electrons magnetic field relative to an outside magnetic field
Magnetic quantum number
Indicates the orientations of orbitals around the nucleus
Significant #? 3
Infinite
If the difference in electronegativity is greater than 2.1, the bond is usually
Ionic
The _______ are in the s and p blocks
Main group elements
Explain the difference between mass and weight
Mass is constant regardless of ones location in the universe, while weight of dependent upon gravity.
Describe 2 characteristics properties of matter
Matter has mass and volume
Temperature?
Measure of how hot/cold something is
The shared electrons move in the space surrounding the nuclei, called the
Molecular orbital
How does an atom differ from a molecule
Molecules consist of two or more atoms joined to each other chemically
Rutherfords model of an atom
Moved in circular orbits
Symbol for nitrogen
N
Mass number
Number of particles in nucleis
Atomic number
Number of protons in nucleus
Allotrope
One of a number of different molecular forms of an element in the same state
Method Mendeleev used to organize elements
Organized on atomic mass
The type and arrangement of [particles/crystals] in sample of matter determine the properties of matter.
Particles
Is ice melting physical or chemical?
Physical
[Physical/Chemical] changes are changes in which the identity of a substance does not change.
Physical
When electronegativity values differ significantly, the two atoms form a
Polar covalent bond
The terms odorless and colorless and _____ terms
Qualitative
Explain the difference between quantity and unit
Quantity is a measure of magnitude, size, or amount as in volume and distance. Unit is a standard used to measure a quantity
How does one determine the location of an atoms electrons?
Quantum numbers tell the main energy level, the shape of the orbital, the orientation of the orbital and the orientation of an electrons magnetic field
In the word equation hydrogen + oxygen + heat -> water, hydrogen is a [reactant/product] and water is a [reactant/product]. This is a chemical change.
Reactant; product
Symbol for sulfur
S
After a chemical reaction, the [same/different] atoms are present in the product.
Same
A nonpolar covalent bond is a covalent bond in which the electrons involved are
Shared equally
Hund's rule
States that for ah sim in the ground state, the number of impaired electrons is the maximum possible and these unpaired electrons have the same spin
Coulombs law
States that the closet two chargers are, the greater the force between them
Aufbau principle
States that the structure of each successive element is obtained by adding one proton to the nucleus of the atom and one electron to the lowest energy orbital that is available
Pauli Exclusion property
States that two particles of a certain class cannot be in the same energy state
Avogadro's number
The # of atoms in 1 mol
Mole
The SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms In 12 grams of carbon-12
Electron configuration
The arrangement of electrons in an atom
Existence of neutrons
The atom too big
Cathode
The electrode attached to the negative terminal of a voltage source
Anode
The electrode attached to the positive terminal of a voltage source
Ground state
The lowest energy state of a quantized system
Molar mass
The mass in grams of one mole of a substance
Atomic mass
The mass of an atom expressed in atomic mass units
Atomic number
The number of protons that compose the nucleus of an atom
Neither atom will remove the electron from
The other atom
Quantum theory
The present day model of the atpm
Why is it important to publish the results of research findings?
The result must be verifiable
What special meaning does the slope of a graph of mass versus volume have?
The slope of a volume-mass graph is the mass per unit volume, or the density of a material.
Line emission spectrum
The spectrum of a few colors seen through a prism made when high voltage current is passed through a tube of hydrogen gas at low pressure
Mass number
The sum of the number of protons and neutrons of the nucleus of an atom
Why are main-group elements called the representative elements?
They are regular and consistent
Why are some #s unlimited?
They aren't measured but counted
Why are valence electrons important?
They define how reactive they are
Law of definite proportions
This states that a chemical compound always contains the same elements in exactly the same proportions by weight or mass
Atomic theory
This states that atoms are the building blocks of all matter
Law of multiple proportions
This states that mass cannot be created or destroyed during ordinary chemical and physical changes.
Evidence for the existence of electrons
Thomson's experiments shows that a cathode ray consists of particles and they have a mass and a negative charge
Most of the matter you encounter is one of [numerous/three] states of matter.
Three
Particles that make up solids are held [loosely/tightly] in a [flexible/rigid] structure, so the particles can [vibrate only slightly/flow past each other]
Tightly; rigid; vibrate only slightly
Gases have a [variable/fixed] volume and shape
Variable
Liquids have a [variable/fixed] volume
Variable
Photoelectric effect
What occurs when light strikes a metal and electrons are released
When is a sample of matter considered a pure substance?
When it is made up of only one atom or molecule
How did Moseley contribute to periodic table
X ray spectra lines line up with atomic number
Bonding causes a decrease in energy for the ....
atoms involved
Unstable atoms become more stable when they
become compounds
Electrons transfer from one atom to another to form?
charged ions
When an ionic bond forms,
electrons are rearranged.
When a covalent bond forms,
electrons are shared between atoms.
Method Newlands used to organize elements
organized based on same properties
Both of the atoms are the same element,
so the forces are equal.
Law of conservation of energy
the total amount of energy remains constant in an isolated system. It implies that energy can neither be created nor destroyed, but can be change from one form to another.
Existence of protons
they repel alpha particles in gold foil experiment
A molecular orbital is made when
two atomic orbitals overlap
Lewis electron-dot structures are used to represent the ?
valence electrons of atoms