Chemistry Atoms Elements and Mixtures Flashcards
(21 cards)
What is an element?
A substance made of only one type of atom.
What is a compound?
Two or more different types of atom chemically bonded together.
What is a mixture?
Two or more different types of atom or compound chemically bonded together.
What is a molecule?
When atoms bond together, the group of combined atoms is called a molecule. They can be elements or compounds.
What are the relative masses of protons, neutrons and electrons?
Proton- 1
Neutron- 1
Electron- 0
What are the relative charges of protons, neutrons and electrons?
Proton- +1
Neutron- 0
Electron- -1
What is the mass number?
The number of protons and neutrons.
What is the atomic number?
The number of protons. It defines what element the atom is.
What is an isotope?
Atoms of the same element which have different numbers of neutrons.
What is the relative atomic mass(Ar) of an atom.
The average mass of an element, as different isotopes have different masses.
What is the formula for relative atomic mass(Ar)?
Ar=((mass of isotope1%common) +(mass of isotope2%common)) /100
What atoms have the same amount of electrons on their outer shell?
Atoms in the same group (column).
What atoms have the same amount of shells?
Atoms in the same period (row).
Who believed that atoms were tiny indivisible particles.
Democritus
Who discovered that compounds are in a fixed ratio?
John Dalton.
Who discovered electrons?
J J Thomson
What is the “plum pudding” model and who thought of it?
A mass of positive charge with negative electrons scattered throughout it. Created by J J Thomson.
Who discovered that the positive charge in an atom is concentrated in a very small nucleus?
Ernest Rutherford
What did Niels Bohr discover?
The electrons are found at specific energy levels of shells.
Who discovered that there are also neutrons in the nucleus?
James Chadwick
What is an ion?
An atom with a positive or negative charge.
