ch 171 - chapter 2 (atoms & molecules)

Atoms are made of what?

Numerous smaller particles (protons, neutrons, electrons)

Protons

Positively charged particles

Neutrons

the particles of the nucleus that have no charge

Electrons

Negatively charged particles

Where are protons and neutrons located?

inside the nucleus

Where are electrons located?

electron cloud (outside the nucleus)

What is the relative mass of protons and neutrons?

1 amu

What is the relative mass of electrons?

1/1840 amu

Most elements in their natural state are made of what?

More than one kind of atom.

Isotope

Atoms of the same element that have different numbers of neutrons.

Atomic weight

Average of the mass numbers of all isotopes (protons + neutrons)

What is the unit for atomic weight?

atomic mass unit (amu)

Relative masses for molecules

Molecular weights, determined by adding the atomic weights of the atoms making up the molecules

Avigadros number of the atoms of an element has a mass in grams equal to...

...the atomic weight of the element

Avogadros number of molecules has a mass in grams equal to...

...the molecular weight

Avogadro's number of particles is called what?

A mole, abbreviated mol

what number reveals the total number of protons and neutrons in the nucelus of an isotope.

mass number, A

atomic number

z, the number of protons/neutrons in an element

exact number

counted or defined. NOT measured typically.

molecular formula

a chemical formula that gives the total number of atoms of each element present in a molecule. (molecular weight in amu usually/empirical mass) gives you the factor to multiply the empirical formula by

empirical formula

show the simplest whole-number ratio of atoms in a compound. get mols of each element in the compound, divide by the smallest number of mols, and whatever number you get is how many molecules of that element are in the empirical formula. u can multiply everything by 2 if the numbers aren’t whole, like if its 1.5)