• The mass of an atom is?concentrated?in the nucleus, because the nucleus contains the heaviest subatomic particles (the neutrons and protons)
  • The mass of the electron is negligible

   

• The nucleus is also?positively?charged?due to the protons
• Electrons orbit the nucleus of the atom, contributing very little to its overall mass, but creating a?‘cloud’?of negative charge
• The?electrostatic?attraction?between the?positive nucleus?and?negatively charged electrons?orbiting around it is what holds an atom together

The mass of the atom is concentrated in the positively charged nucleus which is attracted to the negatively charged electrons orbiting around it

• An atom is?neutral?and has no overall charge
• Ions on the other hand are formed when atoms either?gain?or?lose?electrons, causing them to become?charged
• The number of?subatomic particles?in atoms and ions can be determined given their atomic (proton) number, mass (nucleon) number and charge

Protons

• The atomic number of an atom and ion determines which element it is
• Therefore, all atoms and ions of the?same element?have the same number of protons (atomic number) in the nucleus
  • E.g. lithium has an atomic number of 3 (three protons) whereas beryllium has atomic number of 4 (4 protons)

   

• The number of protons equals the?atomic (proton) number
• The number of protons of an?unknown?element can be calculated by using its mass number and number of neutrons:

Mass number = number of protons + number of neutrons

Number of protons = mass number - number of neutrons

Answers

Answer 1:?The atomic number of a magnesium atom is 12 indicating that the number of protons in the magnesium element is 12

• • Therefore the number of protons in a?Mg2+?ion?is also 12

   

Answer 2:?The atomic number of a carbon atom is 6 indicating that a?carbon atom?has 6 protons in its nucleus

Answer 3:?Use the formula to calculate the number of protons

Number of protons = mass number - number of neutrons

Number of protons = 63 - 34

Number of protons = 29

• • Element X?is therefore copper

   

Electrons

• An atom is?neutral?and therefore has the?same?number of?protons?and?electrons
• Ions have a different number of electrons to their atomic number depending on their charge
  • A positively charged ion has?lost?electrons and therefore has?fewer?electrons than protons
  • A negatively charged ion has?gained?electrons and therefore has?more?electrons than protons

   

Answers

Answer 1:?The atomic number of a magnesium atom is 12 suggesting that the number of protons in the?neutral?magnesium?atom?is 12

• • However, the 2+ charge in Mg2+?ion suggests it has?lost?two electrons
  • It only has 10 electrons left now

   

Answer 2:?The atomic number of a carbon atom is 6 suggesting that the?neutral?carbon?atom?has 6 electrons orbiting around the nucleus

Answer 3:?The number of protons of element?X?can be calculated by:

Number of protons = mass number - number of neutrons

Number of protons = 63 - 34

Number of protons = 29

• • The?neutral atom?of element?X? therefore also has 29 electrons

   

Neutrons

• The?mass?and?atomic?numbers?can be used to find the number of?neutrons?in?ions?and?atoms:

Number of neutrons = mass number (A) - number of protons (Z)

Answers

Answer 1:?The atomic number of a magnesium atom is 12 and its mass number is 24

Number of neutrons = mass number (A) - number of protons (Z)

Number of neutrons = 24 - 12

Number of neutrons = 12

• • The?Mg2+?ion?has 12 neutrons in its nucleus

   

Answer 2:?The atomic number of a carbon atom is 6 and its mass number is 12

Number of neutrons = mass number (A) - number of protons (Z)

Number of neutrons = 12 - 6

Number of neutrons = 6

• • The?carbon atom?has 6 neutrons in its nucleus

   

Answer 3:?The atomic number of an element?X?atom is 29 and its mass number is 63

Number of neutrons = mass number (A) - number of protons (Z)

Number of neutrons = 63 - 29

Number of neutrons = 34

• • The?neutral atom?of element?X?has 34 neutrons in its nucleus

   

• Isotopes are atoms of the?same?element?that contain the same number of?protons?and electrons but a different number of?neutrons
• The symbol for an isotope is the?chemical?symbol?(or?word) followed by a?dash?and then the?mass?number
  • E.g. carbon-12 and carbon-14 are isotopes of carbon containing 6 and 8 neutrons respectively

   

The atomic structure and symbols of the three isotopes of hydrogen

• Isotopes have the?same?chemical properties?but?different physical properties

Chemical properties

• Isotopes of the same element display the?same chemical characteristics
• This is because they have the same number of electrons in their?outer?shells
• Electrons take part in?chemical reactions?and therefore determine the?chemistry?of an atom

Physical properties

• The only difference between isotopes is the number of?neutrons
• Since these are neutral subatomic particles, they only add?mass?to the atom
• As a result of this, isotopes have different?physical properties?such as small differences in their?mass?and?density

• Isotopes?are different atoms of the?same?element?that contain the same number of?protons?and electrons but a different number of?neutrons.
  • These are atoms of the same?elements?but with different mass numbers

   

• Because of this, the mass of an element is given as?relative atomic mass (Ar)?by using the average mass of the isotopes
• The relative atomic mass of an element can be calculated by using the?relative abundance?values
  • The relative abundance of an isotope is either given or can be read off the mass spectrum
  • 

   

Answer

The correct answer option is 1

• • 
  • Ar?= 16.0044
  • Ar?= 16.00

Answer