Atomic Structure

Question 1

What is an atom?

Answer 1

Smallest particle of matter.

building block of all material

Question 2

What did Democritus proposed about the atom in 400-300 B.C.?

Answer 2

Atom is tiny, hard and uncuttable.
Shapes of atoms explain behaviors of elements.
Atoms of water are round balls.
Atoms of fire has sharp edges

Question 3

John Dalton proposal about the atom in 1803

Answer 3

Solid, indivisible sphere. Can’t be created nor destroyed.

“Billiard Ball Model”

Question 4

What did J.J Thomson propose about the atom in 1897?

Answer 4

Atom is a sphere of positive charged particles, containing a few negatively charged particles called electrons.
They are distributed in sphere like “Plum Pudding”.

Question 5

Rutherford’s proposal of the atom in 1909

Answer 5

Divisible units composed of positive charges conc. at nucleus w/ negative charges orbiting around nucleus.

Question 6

Niels Bohr’s proposal of the atom in 1913

Answer 6

Electrons in atoms are restricted to certain circular orbit about the nucleus.
“Planetary Model”
Similar to planets orbiting the sun

Question 7

Schrodinger’s proposal on the atom from 1926-present

Answer 7

• electrons are found in different clouds of energy levels.
• probability of finding e-s w/in a space surrounding the nucleus.
• cloud is denser where probability of finding e-s is high.

Question 8

How do you find the total number of neutrons in an element?

Answer 8

of neutrons= atomic mass - atomic number

Question 9

What are Ions?

Answer 9

Atoms that have either lost or gained an electron.

- charged particles

Question 10

What is an Isotope?

Answer 10

Is an atom that has the same number of protons but different number of neutrons.

eg.: Protium, Deuterium and Tritium