GEN CHEM: Atomic & Molecular Structure – Flashcards

Chemistry is the study of the nature and behavior or matter.

1. Protons

2. Neutrons

3. Electrons

• All elements are composed of atoms. All atoms of a given element are identical in size, mass, ; chemical properties. The atoms of one element are different from atoms of all other elements.
• All compounds are composed of atoms with more than one element. For any given compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction.
• A given chemical reaction involves only the separation, combination or rearrangement of atoms; it does NOT result in the creation or destruction.

• Protons carry a positive charge
• 1 proton = 1 atomic mass unit (AMU or u) = 1 dalton (Da)
• the Atomic number (Z) of an element is equal to the number of protons of that element.
• Positively charged particles carry the same QUANTITY of charge as an electron, but have a mass that is ~1,840x greater than an e-.
• Mass of nucleus of an atom comprises of entire weight of an atom, it only occupies 10^-13 of the volume of the atom.

• Neutrons have no charge
• Have a mass that is slightly larger than that of a proton = ~1 u
• Different isotopes of one element have different number of neutrons but the same number of protons.

• Electrons carry a negative charge.
• Electrons mass is 1/1,837 the mass of a proton or neutron

• Valence electrons are the electrons on the outer most shell of an atom.
• the furthest from the nucleus, the weaker the attractive force of the positively charged nucleus and the more likely the valence electrons are influenced by other atoms.

• Neutral atom have the same number of electrons as protons.

The number of electrons in a neutral atom. 

• An Ion is a result of a positive or negative charge on an atom.
• a + is a loss of an electron
• a - indicated the gain of an electron

• Nickel has an atomic number of 28 ; mass number of 58.
• NI-58 has 28 Electrons, 28 protons and 30 Neutrons (58-28=30)
• nickle-60^2+ has 26 electrons, 28 protons, 32 neutrons (30+2 neutrons = 32)

Atomic Mass number (A) is the sum of nucleons (protons + neutrons)

A superscript, Z subscript before X is written to show.

A= Atomic Mass number

Z= Atomic number

X= atom

The Molecular weight is the weight in grams per one mole (mol) of a given element (g/mol).

A mole is a unit used to count particles and is represented by Avogadro's number 6.02 X10^23 particles/mol.

 Avogadro's number is determined by how many atoms of carbon are in 12.0 g of carbon-12.

Isotopes with the same number of electrons and protons are similar in chemical properties.

14 g

An isotope is an atom that has the same number of protons (same atomic number, z) but has different number of neutrons.

1) Carbon 12, 6 p+ and 6 n

2) Carbon 14, 6 p+ and 8 n

The isotopes are usually present in the same proportions in any same of any naturally occurring element

A weighted average of all the isotopes of an element found naturally on Earth. Found on the table of elements.

40 u (.6) + 44 u(.25) + 4 u(.15)

= 24 u + 11 u + 6.15 u

= 41.15 u

Ernest Rutherford in 1911

Quantum theory proposes that energy emitted as electromagnetic radiation from matter comes in discrete bundles called quanta.

E= hf

h is a proportionality constant = Planck's Constant

Planck's constant = 6.626 x 10^-34 J s

f (sometimes designated as v) is the frequency of the radiation.