Chemistry Midterm

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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


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