Atoms, Elements and Compounds Flashcards
Define element
A substance made up of only one type of atom that cannot be broken down into anything simpler.
What is the symbol for beryllium?
Be
What is the symbol for boron?
B
What’s the symbol for silicon?
Si
Which 7 elements are diatomic?
Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine and Iodine
What is the relative mass of an electron?
1/1840
What is the atomic number and where is it found?
The number of protons in an atom.
Found underneath the element symbol.
(Same as number of electrons)
What is the mass number and where is it found?
The sum of protons and neutrons in an atom.
Found above the element symbol.
Who proposed that matter could not be broken down into smaller pieces forever and was made from small particles called atoms meaning indivisible?
Democritus
What did John Dalton’s atomic theory state?
• Atoms are tiny, invisible particles.
. Atoms of one element are all the same.
• Atoms of different elements are different.
• Compounds are formed by combining atoms.
What year did John Dalton introduce his theory?
1808
Who discovered electrons and when?
J.J Thompson in 1897
What did Ernest Rutherford conclude from his gold foil experiment?
• Atoms are 99% atom space
•The nucleus
• Protons
What did Niels Bohr discover and when?
Electron shells (He came up with the modern model of an atom). In 1913
Who discovered the neutron and when?
James Chadwick in 1932
What are groups in the periodic table and what do they tell us about the elements in them?
The columns and they tell us how many electrons are in the outer shell.
What are the rows of the periodic table called and what do they tell us?
Periods and they tell us the number of electron shells.
What are isotopes?
Atoms with the same number of protons but with different number of neutrons
How do you calculate relative atomic mass?
Ar = (relative isotopic mass 1 x %) + (relative isotopic mass 2 x %)
/100
Define compound
A compound is a pure substance made of different types of atom that have been chemically bonded in a fixed ratio
Define mixture
A mixture is made of at least two substances together that have not been chemically combined
By which bonding do a metal and non metal join together?
Ionic bonding - metals form positive ions and non-metals form negative ions
By which bonding do two or more non- metals join together?
Covalent bonding- molecules are formed which do not have a charge
When is a substance a molecule?
When two or more non metals join together by covalent bonding
OR
When an element is diatomic
