(term 1) Test 1 + 2 Chemistry (Exam)

Precision

A set of data that is close to each other but not necessarily on the target.

Accuracy

A measurement that is close to the true value or target but may not be precise.

Percent error

A calculation used to determine the accuracy of a measurement compared to a theoretical value, expressed as a percentage.

Matter

Anything that takes up space and has mass.

Element

A pure substance that cannot be broken down into simpler substances through chemical reactions.

Compound

A substance formed by two or more elements that are chemically bonded together.

Mixture

A physical combination of two or more pure substances.

Heterogeneous mixture

A mixture that has a visibly different composition and individual substances can be observed.

Homogeneous mixture

A mixture in which the components are uniformly distributed and cannot easily be distinguished.

Physical properties

Characteristics of a substance that can be observed or measured without changing its chemical composition.

Chemical properties

Characteristics that can only be observed during a chemical reaction, involving a change in chemical composition.

Physical change

A change in the form or state of a substance without any change in its chemical composition.

Chemical change

A change that transforms one or more substances into new substances with different chemical properties.

Periodic table

A tabular arrangement of the chemical elements organized by increasing atomic number.

Atom

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

Dalton's Atomic Theory

A theory that posits that all matter is made up of atoms, which are indivisible and indestructible, and that atoms of a given element are identical.

Electron configuration

The distribution of electrons in an atom or molecule's orbitals.

Cation

A positively charged ion that results from the loss of one or more electrons.

Anion

A negatively charged ion that results from the gain of one or more electrons.

Ionic bonding

The electrostatic attraction between positively and negatively charged ions.

Octet rule

The principle that atoms tend to gain, lose, or share electrons to achieve a full outer shell of eight electrons.

Examples of physical changes.

Cutting/Breaking/Sand+water/salt +water /sugar+water/crystallization/Stretching/Crushing/

Crumpling/melting/freezing/boiling/Mixing (if it can be separated/Boiling water

Examples of chemical changes.

• Smell (if it suddenly changes)

• Digestion (acids help break down)

• Combustion (explosion)

• Baking (using yeast to rise a food)

• Leaves changing color

• Rusting

• Rotting 

• Temperature change 

• Photosynthesis

• Sour milk

Dimitri Mendelev

attempted to come up with a system to organize all known elements, he grouped them in order by their individual masses, from the lightest-heaviest. These masses would become known as atomic masses. He put elements in columns based on having similar properties

Groups

They are vertical and contain elements similar to each other.

periods

Do not have a relationship, only in that period because of the increasing atomic mass order.

Metals

everything to the left of the staircase except for hydrogen

Metal Properties

• They tend to have high melting points 

• They are good conductors of electricity and heat

• They are very shiny

• They are very malleable (bendable/shapeable)

• As you go down the chart they get more reactive

Nonmetals

To the right of the staircase

• can be gasses, liquids, or solids but mostly gasses

• If they are solid they are brittle with low melting points and very dull and bad conductors of electricity

• For non-metals, they get more reactive as you go up the chart

Metalloids

Have properties of metals and nonmetals

Law of Conservation of Mass

Mass is not created nor destroyed.

Law of Definite Proportions

a chemical compound that always contains the same elements in the same proportions by mass, every compound is built the same way every time

Law of Multiple Proportions

about multiple compounds made from the same elements. When two elements form more than one compound the ratios of the masses of one element that combine with a fixed mass of the other element are small whole numbers. They come in whole pieces called atoms 

Define the Atomic Theory

1. All matter is made up of atoms. -> law of multiple proportions, atoms are indivisible and indestructible -> law of conservation of mass, 

2. All atoms of a given element are identical in mass and properties ->law of multiple proportions

3. Compounds are formed by a combination of two or more different kinds of atoms in fixed proportions ->law of definite proportions

4. In a chemical reaction, atoms can only be separated, combined, or rearranged ->law of conservation of mass

Who discovered electrons

JJ Thompson

Plum Pudding Model

JJ Thompson created it, its was a bad model because it did not include a nucleas. He also believed electrons where negative.

Rutherfords Gold Foil Experiment

Ernest Rutherford did it, it used alpha particles which where shot through a sheet of gold foil and they would sometimes deflect. This led to the discovery of the nucleas.

Nucleas

It is small, heavy, and positively charged

Protons

are positive, located in the nucleas, weigh the same as nuetrons

Electrons

Are found in the electron cloud outside of the nucleas, they are negatively charged and weigh a lot less than protons and neutrons.

Nucleas

The nucleus weight the same as protons, and are neutral in charge (0), and located in the center of the atom

Nuetrons

are neutral and found in the electron cloud

Atomic Mass

Is a sum of protons and neutrons. it can be written like this carbon-12 (6 protons and 6 nuetrons) In the symbol it is placed on the upper left hand side.

Ground State

• electrons in their lowest possible energy

Orbit # Formula

2n² (n=shell #)

Periodicity

the idea that columns on the periodic table have similar properties

*when they have these similar properties they will have a similar number of valence electrons 

Excited state

• higher energy level than the ground state 

relaxation

When an atom transfers from an excited state energy state to a ground state, by transferring energy to other atoms or through emission

Emission

when the frequency of radiation due to electrons transitioning from a high to low energy state, one of the multiple ways to do that 

Electron Configuration

• The shell's names go in order of s, p,d, f.

• row/shell, where an electron is found 

• Remember when you are in your d-block row you will lose 1 row 

• When you are in the f-block row you lose 2 rows

Stabilizing Metals

• Metals lose electrons and non-metals gain them

• When negative ions are added to an atom it gets bigger and when positive ions are added to an atom it gets smaller