Chem chapter 2 test
A proton is ______________ charged
+
charge of an electron
-
Dalton
atomic theory
What did Democritus believe?
atoms were indivisible and indestructible
Thomson
discovered the electron, plum pudding model, cathode ray tube
For an atom to be neutral, it must have an __________ number of protons and electrons.
equal
The law of definite proportions states that, in any chemical compound...
every chemical compound contains fixed and constant proportions (by mass) of its constituent elements
How is the atomic mass unit (amu) defined?
1/12 the mass of a carbon-12 atom
How many more times massive is a proton than an electron?
1836 times
Formaldehyde contains approximately 53% oxygen by mass. What is the mass of oxygen given 120.6 grams of formaldehyde?
64 g
Dalton's atomic theory that is NOT accepted today include:
Atoms are destructible (think nuclear reactions) In chemical reactions chemical bonds are rearranged Atoms of the same element can be different (isotopes)
Rutherford
Gold foil experiment, discovered nucleus
What is one way to represent the type of gold that has a mass number of 197?
Gold-197
Democritus
Greek, first to hypothesize that matter is composed of indestructible particles called atoms with empty space between those particles
The law of multiple proportions states that whenever the same two elements form more than one compound, the different masses of one element combine with the same mass of the other element...
In whole number ratios
atomic theory
Matter is made up of atoms Atoms are indestructible Atoms of the same element are identical Atoms of different elements are different In chemical reactions atoms are rearranged
What is the atomic number of an element?
Numerically equal to the number of protons in the nucleus of an atom of that element, identifies the element
Why are isotopes chemically alike?
They are the same element, they have the same number of protons and electrons (if neutral)
Isotopes have different mass numbers because:
They have different numbers of neutrons
Levoisier
law of conservation of mass
Proust
law of definite proportions
Elements are different because they contain different numbers of __________.
neutrons
Most of the mass of an atom is concentrated in its __________.
nucleus
Location of an electron in an atom
outside the nucleus
Neutrons have no charge and have a mass nearly equal to that of a __________.
proton
How is mass number calculated?
protons + neutrons
To calculate the atomic mass of an element, what two things must you do?
you must multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products
