5.1.1.1 atoms, elements and compounds Flashcards
What is an atom
An atom is the smallest part of an element that can exist- all substances are made of atoms.
Atoms of each element are represented by a_________ ________
Chemical symbol
How many elements are there approximately?
100
How are compounds formed? What are they?
They are formed from elements by chemical reactions. Compounds contain two or more elements chemically combined in fixed proportions. They are represented by the formulae from the symbols of the atoms they were formed from.
What are chemical reactions?
They always involve the formation of one or more new substances, and often involve a detectable energy change
Atoms have a small central nucleus, which is made up of _______ and _______ around which there are ________ on rings.
Protons, neutrons, electrons
What is the mass and charge of a proton?
Mass- 1 charge - +1
What is the mass and charge of a neutron?
Mass - 1 charge - 0
What is the mass and charge of an electron?
Mass - almost 0 mass - -1
What is the mass number of an element?
Total number of protons and neutrons, this is the top number.
Quay is the atomic number of an element?
Number of protons (/electrons),
This is the bottom number.
What is an isotope?
each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei
Who were the Greek scientists?
Leucippus and Democritus
What year did John dalton produce is theory and what is the theory?
1803, All matter is composed of extremely small particles called atoms
What year did J J Thompson produce his theory and what is his theory?
1897, all atoms contain tiny negatively charged subatomic particles or electrons.
(Plum pudding model)
