chap 3

law of conservation of mass

States that matter can be neither destroyed nor created during ordinary chemical reactions or physical changes

law of definite proportions

The fact that a chemical compounds contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

law of multiple proportions

if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

atom

the smallest particle of an element that retains the chemical properties of that element

nucleus

very small region located near the center of an atom

proton

positively charged particle

neutron

neutral particle

electron

negatively charged particle

cathode ray tube

Experiments in which electric current was passed through various gases at low pressures. Experiments were carried out in glass tubes called (blank).

nuclear forces

short range proton-neutron, proton-proton and neutron-neutron forces holding the nuclear particles together

atomic number

the number of protons in the nucleus of each atom of an element

isotope

atom of the same element with a different mass

mass number

total number of protons and neutrons in the nucleus of an isotope

nuclide

general term for any isotope of any element

atomic mass unit

exactly 1/12 the mass of a carbon-12 atom

average atomic mass

the weighted average of the atomic masses of naturally occurring isotopes of an element

mole

the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12

Avogadro's number

6.022 x 10^23. The number of particles in exactly one mole of a pure substance.

molar mass

the mass of one mole of a pure substance

chemical reaction

transformation of a substance or substances into one or more new substances

John Dalton

proposed an atomic theory

Joseph Proust

established the Law of definite proportions.

Antoine Lavoisier

established the Law of conversation of mass.

Democritus

stated that the universe was made of invisible units called atoms (unable to be divided) & believed movements in atoms caused changes observed in matter

Dalton's atomic theory laws mentioned.

* Each element is composed of extremely small particles called atoms.
\-Atoms of the same element are exactly alike in size. mass, and properties.
\-A chemical rxn is a rearrangement of atoms; atoms can not be subdivided, created, or destroyed.
\-Every compound always has the same ratio and kinds of atoms.

Dalton's Errors in Theory

* all atoms of the same element have the same mass.


* atoms cannot be subdivided.

negative particles

The behavior of cathode rays in a glass tube containing gas at low pressure led scientists to conclude that the rays were composed of

Dalton

The basic principles of the atomic theory that are still recognized today were first conceived by

mass number

Atoms of the same element can differ in

can not be created or destroyed

Dalton's atomic theory helped to explain the law of conservation of mass because it stated that atoms

Milliken's experiments

determined the approximate value of the electron's mass.

electron cloud

Most of the volume of an atom is made up of the \________

definite proportions

If a particular compound is composed of elements A and B, the ratio of the mass of B to the mass of A will always be the same. This is a statement of the law of....

electrons

Since any metal cathode used in a cathode-ray tube produced the same charged particles, it was concluded that all atoms contain...

isotopes

Atoms of one or same element that have different masses are called

mass

the total number of protons and neutrons in the nucleus of an isotope is called its \__________ number.

atomic

The number of protons in the nucleus of an element is called its \_________ number.

If two or more compounds are composed of elements A and B, the ratio of the masses of B combined with 1g of A make each compound a ratio of small whole numbers. This is a statement of the law of \___________

multiple proportions

What is molar mass? How is it related to atomic mass?

\-mass of one mole of a substance

\-the atomic mass is a mass on one atom + there are 6.022x10^23 atoms in every one mole.

atomic mass of a single isotope is its relative mass compared to the mass of carbon-12. the average atomic mass is the weighted average of masses of all naturally occurring isotopes of an element.

Explain why the atomic mass of a particular isotope of an element differs from the average atomic mass of that element.