atoms and periodic table

1. Democritus proposed the atom

2. modern atomic theory - M.A.D. C.A(D,M)P 3 3 (law of conservation of matter, law of definite proportions, law of multiple proportions) CONSERVATION AND PROPORTIONS

3. dalton’s atomic theory ELEMENTS MADE OF ATOMS / ELEMENT ATOMS DIFF FROM EACH OTHER, ATOMS CAN COMBINE, COMBINE IN WHOLE NUMBER RATIOS, FORM COMPOUNDS! / ATOMS ARE UNCHANGED IN CHEMICAL REACTION

   1. elements are made of tiny indivisible particles aka ATOMS

   2. atoms of each element are unique to each other

   3. atoms can join together (combine) in whole number ratios to form compounds

   4. atoms are unchanged in chemical reaction

   5. mass: 1 atomic mass unit (amu) = 1.67 × 10^-27

   6. 1 hydrogen atom = 1 amu, 1.67 × 10^-27 kg

      • todays amu is based specifically on Carbon-12, most abundant element on earth = 12.00 amu exactly, where amu scale comes from

   • like charges repel, opposite attract. to be electrically neutral, something must have no charge whatsoever, OR equal amounts of opposite charges

     • ATOMS HAVE NO CHARGE

     • = OPPOSITE CHARGES

4. JJ Thompson ELECTRON DISCOVERY, PLUM PUDDING MODEL

5. Ernest Rutherford gold foil experiment, nuclear model

   1. Protons were discovered by Ernest Rutherford (often cited around 1917–1920) through experiments with alpha particles, while neutrons were discovered by James Chadwick in 1932. Both particles are located in the nucleus, with Chadwick confirming the existence of the neutral particle Rutherford had previously theorized. 

6. Dimitri Mendeleev PERIODIC TABLE

   • arranged elements by INCREASING ATOMIC MASS; REPEATING PATTERNS OF PROPERTIES EMERGE

     • “periodic pattern”

Democritus

BCE time period, wasnt accepted until early 1800s

• said atom is indivisible; there is no smaller part than an atom (there is a finite ending

Modern Atomic Theory

3 laws led to the development and acceptance of this

1. law of conservation of matter: MATTER CANNOT BE CREATED NOR DESTROYED; reactants = products

2. law of definite proportions: COMPOUNDS DISPLAY CONSTANT COMPOSITION; compounds will always have the same chemical formulas

3. law of multiple proportions: ATOMS COMBINE IN WHOLE NUMBER RATIOS ONLY

law of conversation of matter, law of definite proportions, law of multiple proportions

Dalton’s Atomic Theory

1. elements are made of tiny indivisible particles aka ATOMS

2. atoms of each element are unique to each other

3. atoms can join together (combine) in whole number ratios to form compounds

4. atoms are unchanged in chemical reaction

elements made of atoms, elements atoms are unique, atoms can join to form compounds, atoms are unchanged

• AT THIS TIME, IT WAS UNKNOWN THAT ATOMS WERE NOT!! THE SMALLEST. NOT KNOWN THERE WAS SOMETHING SMALLER aka subatomic particles!

Parts of the Atom

• subatomic particles: make up atoms, which makes up elements

Dalton’s Atomic Theory established:

• mass: 1 atomic mass unit (amu) = 1.67 × 10^-27

• 1 hydrogen atom = 1 amu, 1.67 × 10^-27 kg

  • todays amu is based specifically on Carbon-12, most abundant element on earth = 12.00 amu exactly, where amu scale comes from

• like charges repel, opposite attract. to be electrically neutral, something must have no charge whatsoever, OR equal amounts of opposite charges

  • ATOMS HAVE NO CHARGE

  • = OPPOSITE CHARGES

JJ Thompson

late 1800s

• discovered the electron = particle with a negative charge

• the mass = 1/1836 th that of the mass of a hydrogen atom; very small

• the charge has a fundamental unit of charge we designate as -1

• the PLUM PUDDING MODEL = envisioned the electrons spreadthroughout a positively charged material

  • or electrons suspended in a sea of positive charge (neutron not divscovered yet)

    • from 1890’s to start of 20th century

Ernest Rutherford

• what is the middle of my atom? where is the sea of positive charge coming from?

Rutherford Experiment - GOLD FOIL EXPERIMENT

• uses large target atom (heavy), and uses a very small particle as the bullet with a large amount of energy

what did rutherford see?

• 0.01% particles bounced off of the gold foil nOT SUPPOSED TO HAPPEN, THOUGHT TO BE IMPOSSIBLE

  • most go straight through ok, some deflected ok explained from electrons

Nuclear Model CONCLUSION

-something must be inside of my atom causing complete deflections, but not very large in volume

MOST ALPHA ARTICLES GO STRAIGHT THROUGH, SOME ALPHA PARTICLES GO THROUGH BUT ARE DEFLECTED

VERY FEW OF THE ALPHA PARTICLES DID NOT GO THROUGH

• as a result the atom

  • is mostly empty space with a dense nucleus at the center

  • nucleus is small in volume but contains virtually the entire mass of our atom

nucleus

• protons (positive charge)

• neutron (no charge)

atomic mass

• average weighted mass of an atom based on the percentage abundance of existing isotopes

• ISOTOPES: elements with the same number of protons but different numbers of neutrons

  • DIFF NUMBER OF NEUTRONSSSS I-NN

Periodic Table of Elements

Dimitri Mendeleev

• arranged elements by INCREASING ATOMIC MASS; REPEATING PATTERNS OF PROPERTIES EMERGE

  • “periodic pattern”

• periodic law: properties tended to repeat themselves when arranged by increasing mass

• the pattern was used to ID unknown elements (gallum and geranium)

• when atomic mass oder did not dit, elements recorded by physical properties

Modern periodic table 1917-WWI

• todays elements are arranged by increasing atomic number

• elements with similar PHYSICAL AND CHEMICAL PROPERTIES are found in the same COLUMN = GROUP = FAMILY!!

ROWS = PERIODS

• each period shows pattern of properties repeated in the next rows

Main

main group elements

• “A” group

• elements whose properties are very similar in the column

transition elements

• B group

• elements whose properties are harder to predict based on their position

  • the transition metals = center of periodic table

  • inner transition elements = rare earth elements, lanthanide and actinide series VERY BOTTOM OF TABLE

    • LANTHANIDE ROW 6

    • ACTINIDE ROW 7

Metals

1. 75% elements; all solid at room temp EXCEPT HG (which is liquid, mercury)

2. reflective surface

3. conductor of heat and electricity

4. malleable; shaped easily

5. ductile; pulled or drawn into wires

6. LOSES ELECTRONS to form “CATIONS” in chemical reactions

LEFT, LOWER LEFT, AND MIDDLE OF PERIODIC TABLE

Nonmetals

1. 17, found in all 3 states

solids

1. carbon

2. sulfur

3. selenium

4. phosphurous

5. idoine

liquid

1. bromine

gases

1. H

2. He

3. N

4. O

5. F

6. Ne

7. CL

8. Ar

9. Xe

10. Rn

11. Kr

2. poor conductors of heat and electricy - insulator

3. NOT ductile NOT MALLEABLE (solid nonmetals fracture easily, brittle)

4. GAINS ELECTRONS form “ANIONS”

5. right side of periodic table EXCEPT HYDROGEN, upper left corner

Metalloids

8 in total

• share properties of metal and nonmetals

• semiconductors

• boron, silicon, germanium, arsenic, tellurium, polonium, astantine

• STAIRCASE 3A TO 7A

Families of Periodic Tables

1. Hydrogen

• colorless DIATOMIC gas, (nonmetal low melting point, low density)

• reacts with other nonmetals to form molecular compounds (H2O, CH4)

• reacts with metal elements t oform hydride compounds (NaH, CaH)

• react with water to form hydrogen gas

• many hydrogens compounds dissolved in water from acids

2. Alkali metals (Group 1A except Hydrogen) FAR LEFT

• soft, reactive, react violently in water, react with moisture in air

• catch fire in water, corrosive in the air, lose metallic luster, elements stored under oil

3. Alkaine Earth Metals (Group 2A) FAR LEFT

• less reactive than alkali metals; brn brightly when combined with oxygen

• still very reactive just not as much as 1A

4. Halogen 7A FAR RIGHT

• highly reactive nonmetals; exist as diatomic molecules in nature, form compounds

• react with alkali metals like NaCl table salt

5. Noble Gas 8A FAR RIGHT

• ALL GASES AT ROOM TEMP DUH

• inert DO NOT REACT

• found freely in elemental form, as gases

OTHER MAIN GROUP FAMILIES

• named after first element in the family

group 3a

• boron family

group 4a

• carbon family

group 5a

• nitrogen family

group 6a

• oxygen family

transition metals: metals with mixed varied properties

• lathanide series: stable rare earth metals, stable

• anctinide series: radioactive rare earth metals

Charged Atoms: Ions

• number of protons determines identity; protons + neutrons (A0 determines mass

• in a chemical change, PROTON IN NUCLEUS DOES NOT CHANGE

  • its number of electrons

positive charge = CATIONS (form by losing or removing electrons, typically are your metals)

CATIONS = METALS, LOSE ELCTRONS

metal charge determined by GROUP NUMBER

MAIN GROUP GROUP A TRICK

1A = +1

2a +2

3A +3

negative charge = ANIONS gain electrons NONMETALS

MAIN GROUP GROUP A TRICK

GROUP NUMBER -8 (neg charge)

7A -1 anion HALOGEN

6A -2 anion OXYGEN

5A -3 anion NITROGEN

IONS are very different from their neutral aoms; have diff properties make them behave very similar to atoms in grop 8A (inert, nonreactive)

• NOBLE GASES WILL NEVER FORM IONS!!!