Unit 3 chemistry

History of the atom + Isomotes+ Ions

Democritus

Came up with the idea of the atom

John Dalton

Father of the atom

First atomic theory:

Dalton- Father of Modern Atomic Theory - has four components

1. All matter is made of indivisible atoms- PROVEN WRONG BECAUSE ATOMS ARE DIVISIBLE

2. All atoms of the same element are identical. The atoms of any one element are different

from those of any other element— PROVEN WRONG BECAUSE SUBATOMIC PARTICLES OF THE SAME ELEMENT CAN HAVE DIFFERENT ISOTOPES

3. Atoms of different elements can physically mix together or can chemically combine with

one another in simple whole-number ratios to form compounds (Law of Definite

Proportions)

-applies when 2 or more elements combine to make more than one type of compound

(Law of Multiple Proportions)

4. Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of

one element are never changed into atoms of another element as a result of a chemical

reaction

Thomson

• Used a Cathode ray tube (discovered by Sir. William Crookes) and magnetics discover the electron.

• Found atoms are divisible

• Plum pudding model

Rutherford

• Used gold foil and alpha radiation to discover the proton and nucleus

• Protons inside nucleus and electrons are around

Bohr

Bohr model

• Electrons move in orbits that have a set amount of energy levels

Schrödinger

Quantum Mechanic model

Electron clouds- wave function

Chadwick

• Discovered neutron

• Found that different masses of the same element

Becquerel

• Discovered radioactivity

Alpha Radiation- positive-can be stopped by paper

Beta Radiation- fast moving electrons-can be stopped aluminum foil

Gamma Radiation-no mass, no charge- can be stopped by lead or concrete

Atomic Number

• Number of protons in an atom

• Identifies the element

Mass number

• Number of protons AND neutrons

Atom Mass

the weighted average of the mass of different isotopes of the same element based on their abundance in nature

Nucleus

contains protons and neutrons, takes up very little space, contains the mass of the atom

Electron Cloud

contains electrons, takes up all the volume of the atom

Nuclear Notation

Hyphen Notation

Name of element - mass number (Ex. Carbon-13)

Isotopes

• Isotopes are atoms of the same element that have the same number of protons but different number of neutons.

• Same atomic #, different mass #

Netural atoms

Number of electrons equals to number of protons

Ions

Atoms that have gained or lost electrons

Cation- positive, lost electrons

Anion- negative, gained electrons

Chemical reactions:

1. Definition

2. What happens to the atoms during reactions?

3. The subatomic particles involved during reactions.

4. Energy change (heat) during reactions

5. Factors that influence the speed of reactions

1. Chemical reactions occur when bonds are broken and/or formed

2. No new elements

3. Valence electrons are the only subatomic particles involved during the reaction

4. Small energy change

5. Temperature and catalyst affect speed of chemical reactions

Nuclear reactions

1.Definition

2. What happens to the atoms during reactions?

3. The subatomic particles involved during reactions.

4. Energy change (heat) during reactions

5. Factors that influence the speed of reactions

1. Nuclear reactions Occur when a nucleus emits particles and/or rays

2. New elements are made

3. Protons and neutrons are involved in reaction

4. Large energy change

5. Temperature and catalyst DO NOT influence speed of nuclear reactions

Alpha radiation

• Helium nucleus

• +2 charge, 4 mass,

• slowest

• can be blocked by paper

Beta

• fast moving electrons

• Charge= -1

• Mass= 0

• Medium speed

• Can be blocked by Al foil

Gamma

• High energy electromagnetic radiation

• Light

• Charge=0

• Mass=0

• Fastest

• Can be blocked by lead(Pb) or concrete

Balancing Nuclear Reactions

Balance the mass number (the total of mass numbers on the left is equal to the right)

2. Balance the atomic number (the total of atomic numbers on the left is equal to the right)

3. Take into account the coefficient when applicable.

4. Identify the missing element by using the atomic number

5. Possible missing particles involved in nuclear reactions are:

Fission

• A nucleus splits into multiple nuclei

• Happens in nuclear reaction/ weapon

Fussion

• Two nuclei combine into one nucleus

• Only happens on the star or sun

• More energy produced than fission

• Waste is safer

Dmitri Mendeleev

arranged elements by increasing atomic mass

Mendeleev’s periodic table was in error because as atomic masses became calculated more accurately; it was evident that some elements were placed into groups with differing properties

Henry Moseley

organized the elements by increasing atomic number instead of atomic mass. This arrangement resulted in a clear periodic pattern of properties

Periods

Horizontal rows

Increasing energy levels

Groups

Aka families

Same # of V.E

Most reactive nonmetals

Halogens

Most active metals.

Alki metals

Most active metal

Francium

Most active nonmetal

Fluorine

As you go down metals…

Become more active

As you go down nonmetals become..

Less active