1.2.1 - The Atomic Model

Question 1

What are elements?

Answer 1

substances that can not be broken down into simpler components by chemical reactions

Question 2

What is an atom?

Answer 2

the smallest unit of an element

Question 3

What did John Dalton propose to explain that hydrogen and oxygen always combine in fixed proportions?

Answer 3

all matter is composed of atoms, atoms cannot be created nor destroyed, atoms of the same element are alike in every way, atoms of different elements are different, atoms can combine together to form molecules

Question 4

How was it concluded that the nucleus was very small and the atom is mostly empty space?

Answer 4

Ernest Rutherford fired alpha particles at a piece of gold foil, most went straight through but some were deflected when the alpha particles collide and were repelled by a positive nucleus

Question 5

Why are neutrons important for elements with more than one proton?

Answer 5

without neutrons, the charged protons would repel eachother and the nucleus would fall apart

Question 6

What is the atomic number?

Answer 6

the number describing each element’s relative position on the periodic table and the number of protons

Question 7

What is the atomic number represented by?

Answer 7

Z

Question 8

What is the mass number of an element represented by?

Answer 8

A

Question 9

What is the mass number?

Answer 9

protons + neutrons

Question 10

What is responsible for a chemical change?

Answer 10

electrons only

Question 11

What is an ion?

Answer 11

an atom whose protons are not balanced by the same number of electrons

Question 12

What is a cation?

Answer 12

positive ion (lost electrons)

Question 13

What is an anion?

Answer 13

negative ion (gained electrons)