History of Chemistry
Early people were producing these types of changes even though they didn't know what was happening. For example - extracting metals from ores via smelting or burning wood.
chemical
This is roughly equal to the sum of an atom's protons and neutrons.
atomic mass
This Russian chemist is credited with creating the first widely recognized periodic table, which he arranged by atomic mass.
Dmitri Mendeleev
An element with 6 protons and 7 neutrons is this isotope of carbon.
Carbon-13
Gold's atomic number is _______.
His 1911 gold foil experiment led to the discovery of the atomic nucleus.
Ernest Rutherford
The number of protons an atom has is determined by this number on the periodic table.
atomic number
A mixture like air or a saltwater solution is classified as this type of mixture because its components are evenly distributed.
homogenous mixture
The modern periodic table is arranged based on this property of elements, unlike Mendeleev's original table.
atomic number
These particles are negatively charged and are found outside the nucleus.
electrons
To find the number of neutrons in a specific isotope, you subtract the atomic number from this.
mass number
The process of a liquid becoming a gas, like when a puddle disappears on a sunny day.
vaporization (or evaporation)
This scientist proposed a planetary model of the atom where electrons orbit the nucleus in specific, discrete energy levels.
Niels Bohr
In a neutral atom, the number of these particles is equal to the number of protons. Most of the mass of an atom is located here.
number of electrons
This element has no neutrons in its most common isotope.
hydrogen
This extremely hot state of matter is made of electrically charged particles, found in stars and neon signs.
plasma
Some atoms have more ___________, which makes it an isotope and gives it a negative charge
electrons