Unit 2-Chemistry Flashcards by Nicole Harrison

Define matter

Anything that occupies space and has mass. Found on earth in three physical states : solid liquid and gas

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Define elements

A substance that cannot be broken down to other substances by ordinary chemical means

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What are the four common elements

Oxygen
Carbon
Hydrogen
Nitrogen

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Define a molecule

Formed when two or more atoms are joined chemically

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Define a compound

A substance consisting of two or more different elements combined in a fixed ratio
More common then pure elements

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Define an atom

The smallest unit of matter that still retains the properties of an element

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Define a proton

A subatomic particle with a single positive electrical charge

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Define an electron

A subatomic particle with a single negative charge

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Define a neutron

Has no charge

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Define atomic number

Number of protons in a molecule

Note it’s also the number of electrons

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Define mass number

And atomic mass

The sum of the number of protons and neutrons in its nucleus
Protons and neutrons pretty much weigh the same
Atomic mass is approximately equal to its mass number

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What are two types of ions

Cations (+)

Anions (-)

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Define isotopes

When an element has the same number of protons and behave identically in chemical reactions but they have different numbers of neutrons

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Example of isotopes

Carbon isotopes 
Carbon 12 (6 neutrons)
Carbon 13 (7 neutrons)
Carbon 14 (8 neutrons) 
But they all have the same number of protons (6)

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Stable isotopes

Their nuclei remain intact more or less forever

Ex) C12 an C13

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Radioactive isotopes

When the nucleus decays spontaneously giving off particles and energy
Can cause damage
Ex) C14

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Define electron shells and valence shells

Electron shells= what electrons orbit on

Valence shell= the number of electrons in the outermost shell

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What do valence shells determine

The chemical properties of an atom

Atoms whose outer shells are not full tend to interact with other atoms

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How do chemical interactions between atoms enable them to fill their outer electron shells

When two atoms with incomplete outer shells react each atom will share donate or receive electrons so that both partners end up with completed outer shells

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Chemical bonds

An attraction that holds atoms close together

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What is the strongest kind of chemical bond

Covalent bond

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Define covalent bonds

Two atoms share one or more pairs of outer shell electrons

This forms a molecule

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What is a single covalent bond

The sharing of a pair of electrons

1 electron from each atom

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How many covalent bonds can an atom form?

It depends on the number of additional electrons needed to fill its outer(valence) shell
Ie a double bond

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Define electronegativity

An atoms attraction for shared electrons | The more electronegative an atom the more strongly it pulls shared electrons toward its nucleus

Define non polar covalent bonds and give examples

Electrons are shared equally between the atoms Ex) O2 and H2 the two identical atoms exert an equal pull Methane is non polar because carbon and hydrogen are not much different in electronegativity

What is one of the most electronegative elements | What does this make this atom

Oxygen (Also nitrogen) Oxygen attracts the shared electrons more strongly A polar covalent bond

Define a polar covalent bond | Give an example

The pulling of shared negatively charged electrons closer to the more electronegative atom makes that atom partially negative and the other atom partially positive H2O

Define a polar molecule | Give an example

Has an unequal distribution of charges Negative at water end Positive at hydrogen end

Define an ion

An atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons

Define an ionic bond | Give an example

When an attraction holds two ions with opposite charges together to fill the outer electron shell Electron donations Crystal

Define hydrogen bond | What type of strength are these

When the positively charged region in this type of bond is always hydrogen then we call it a hydrogen bond A hydrogen atom that has formed a polar covalent bond with an electronegative atom had a partial positive charge Weak bonds

What enables neighbouring water molecules to hydrogen bond to one another

The molecules are polar with the negative end (oxygen) of one molecule attracted to a positive end (hydrogen) of its neighbour

Define chemical reaction

The breaking and making of chemical bonds leading to changes in the composition of matter Do not create or destroy matter

Define reactants

Beginning materials of a chemical reaction

Define products

The material resulting from the chemical reaction

Define cohesion

When molecules of the same kind stick together and is much stronger for water. Hydrogen bonds between water

Define adhesion

The clinging of one substance to another

Define heat

The amount of energy associated with the movement of atoms and molecules in a body of matter

Define temperature

Measures the intensity of heat. The average speed of molecules rather then the total amount of heat energy in a body of matter

Define evaporation

Occurs because the molecules with the greater energy leave

Define a solution

A liquid consisting of a uniform mixture of two or more substances

Define a solvent

The dissolving agent

Define a solute

A substance that is dissolved

Define an aqueous solution

When water is the solvent

What are the two ions formed from dissociation of water

``` Hydroxide ions (OH-) Hydrogen ions (H+) They are both very reactive ```

Define acids

More H+ ions | A compound that donates hydrogen ions

Define a base

A compound that accepts hydrogen ions and removes them Donates OH- and that combined with the H+ to form H2O Less H+ ions More OH-

Define a pH scale

``` A scale used to describe how acidic or basic a solution is Ranges from 0-14 0-6= acid 7= neutral 8-14= basic Each notch is x10 H+ ```

Changing the ___ would change it into an atom of a different element

Number of protons in the nucleus of an atom

Your body contains the smallest amount of which element

Phosphorus

A solution at pH 6 contains ___ then the same amount of a solution at pH 8

100 X more H+

Most of the unique properties of water result from the fact that water molecules __

Are polar and form hydrogen bonds

A sulphur atom has 6 electrons in its outer shell. As a result it forms __ covalent bonds with other atoms

Two

What does the word trace mean when you're talking about a trace element

The element is required in very small amounts

A can of cola consists mostly of sugar dissolved in water with some carbon dioxide gas that makes it fuzzy and makes the pH less the 7. In chemical terms you could say the cola is an aqueous solution where water is the __ sugar is a __ and carbon dioxide makes the solution __

Solvent Solute Acidic

Radioisotopes can be used in medical studies because __

Their location or quantity can be determined because of their radioactivity

True or false | Table salt, water, and carbon are compounds

False

True or false | The smallest unit of an element is a molecule

False

True or false | A bathtub full of lukewarm water may hold more heat then a teakettle full of boiling water

True

True or false | If the atoms in a molecule share electrons equally the molecule is said to be non polar

True

True or false | Ice floats because water molecules in ice are more tightly packed then in liquid water

False

True or false | Atoms in a water molecule are held together by the sharing of electrons

True

True or false | Most acid precipitation results from the presence of pollutants from aerosol cans and air conditioners

False

True or false | An atom that has gained or lost electrons is called an ion

True

Define organic compounds

Carbon based molecules

What is one of the simplest organic molecules

Methane

Define hydrocarbons | What are two examples

Compounds composed of only carbon and hydrogen | Methane and propane

Define carbon skeleton

The chain of carbon atoms in an organic molecule

Define isomers

Compounds with the same formula but different structural arrangements

Unit 2-Chemistry Flashcards

(70 cards)