Flashcards in C2.3 Atomic structure etc. Deck (10):

1

## What is the mass number of an atom?

### The total number of protons and neutrons

2

## What is an isotope?

### Isotopes are atoms of the same element that have different mass numbers but the same atomic number

3

## What symbol represents relative atomic mass?

###
Ar

The mass of the particular ATOM

eg K, Na, Rb

4

## What symbol represents relative formula mass?

###
Mr

The mass of the whole molecule

eg H7C13 would be 7 x Ar of H plus 13 x Ar of C

5

## What is one mole of a substance?

### One mole is the Mr / Ar of a substance shown in grams

6

##
If one mole of Carbon monoxide is 28g, how many moles are in

-56g of carbon monoxide

-14g of carbon monoxide

###
56 / 28 = 2

2 moles

14/28 = 0.5

0.5 moles

7

## Why is the Ar for some elements not a whole number (eg chlorine = 35.5)?

###
The Ar is the average atomic mass from all the isotopes of the element

8

## How would you calculate the Ar of Chlorine where 75% have an Ar of 35 and 25% have an Ar of 37?

###
In 100 atoms of chlorine:

75 would be 35

25 would be 37

Find the mean average:

75 x 35 = 2625

25 x 37 = 925

2625 + 925 = 3550

3550 / 100 = 35.5

9

## What is the 'standard atom' that other atoms are relative to?

### Carbon (Ar 12)

10