Simplify the following text for a Grade 10 native English-speaking person.
Original: On his death in 1952 , Elizabeth became Head of the Commonwealth , and queen of seven independent Commonwealth countries : the United Kingdom , Canada , Australia , New Zealand , South Africa , Pakistan , and Ceylon .
Simplified: When Elizabeth became Queen on 6 February 1952 , she was officially Queen of the United Kingdom , Canada , Australia , New Zealand , South Africa , Pakistan and Ceylon ( now called Sri Lanka ) . These were the Commonwealth countries .