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Flashcards in Concepts Of Matter Deck (27):

What are atoms comprised of?

Protons (p^t)
Neutrons (n°)
Electrons (e^-)


Explain pt, n° and e-

Protons are positive and are found in the nucleus of the atom. ~1.00 amu
Electrons are negative and are found in shells (orbits) outside the nucleus. ~1/1837 amu
Neutrons are neutral and are found in the nucleus of the atom. ~1.00 amu


What is the number of electrons called

Atomic number


What do the letter A and Z represent and what is the notation for an atom of any element

A mass number
Z atomic number


Define atomic number, mass number, and atomic mass

Atomic number- number of protons
Atomic Mass- average mass of naturally occurring isotopes of an element
Mass number- the sum of the protons and neutrons


What is the law of the conservation of mass

The law that states that no change is observed in the total mass of the substance involved in a chemical change.
Mass of reactants = mass of products


Define the law of Constance composition (definite composition)

-A natural law is a statement used to summarize the general observation regarding nature
-law of definite composition is used in the case of a composition if compounds. This states that a compound always contains 2 or more elements chemically combined in a definite proportion by mass


Define the law of multiple proportions

-the atom of two or more elements may combine in different ratios to produce more than one compound
-these laws states that
1) the composition of a particular substance will always be the same no matter what it's origin or how it is formed
2) the composition of different compounds formed from the same element will always be unique


Equation for average atomic mass

AAA = (% of mass of isotope 1) + (% of mass of isotope 2)


What are the models and theories that attempted to explain the structure of atoms

Dalton's theory
Thompson's model
Rutherford's model
Bohr's model
Quantum model


What did Dalton's theory propose and which ones were wrong

Matter is made up of tiny particles called atoms
Atoms of different elements are different
*Atoms of the same element are identical
*Atoms are indivisible and indestructible
Atoms of different element combine in simple whole number ratio to form a compound


Why are two theories from Dalton, modified?

1) atoms of the same element are identical
Modified due to the discovery of isotopes, which are atoms of the same element, that have the same atomic number but a different mass number

2) Atoms are indivisible and indestructible
Modified because of subatomic particles and the development of the nuclear bomb


Describe the Thompson model

-based on the result of the cathode ray experiment, Thompson proposed that the atom is a solid, positive mass with negative electron embedded in it
-the model of the atom has been likened to a raisin bun or plum pudding


Describe Rutherford's model

Rutherford conducted the gold foil experiment and suggested that the atom is comprised of a small, dense, positively charged nucleus surrounded by mostly empty space. Electrons exist in this empty space where they orbit the nucleus.


Explain the gold foil experiment and the problems with the Rutherford model

In the gold foil experiment, Rutherford fired alpha (x) particles at gol foils. He expected all of the particles to go through the foil, instead he observed that most went through but some came back and some deflected to the sides

The Rutherford model does not explain why electrons as they move and lose energy does not crash into the nucleus


Describe the Bohr model

-suggested that the nucleus of an atom is surrounded by shells (orbits) where electrons exist in
-these electrons could move from a low energy orbit to a high energy orbit by absorbing energy and vice versa
-the energy of these orbits are quantized; Max Planck was the first person to introduce the concept of quantized energy, while Bohr applied it to his own mode


Problems with the Bohr Model

This model attempts to map the path of electrons, this cannot be done
It only works for hydrogen but cannot explain the spectra obtained for the multi electron atom


What is light spectra and what are the kinds?

The pattern of light obtained when light is analyzed
1) continuous spectra
2) line spectra


Describe continuous and line spectra

Continuous Spectra
- this is the "pattern of light" obtained when light from a mixed source is analyzed (eg sun)
-no breaks between the colours. One flows into the next (rainbow)

Line spectra
- this is the type of spectra you obtain from a single light source (single element eg neon or sodium)


What are the 2 theories of light

Wave theory
Particle theory


Explain the wave theory (concept)

-The wave produced from light in Afro, of electromagnetic radiation.
-Electromagnetic waves occur due to vibrations in an electric and magnetic field and do not need a medium to form unlike other waves


What is a wavelength

Distance from peak to peak or trough to trough (lamda)


Define frequency

Number of waves that pass a given point per unit of time (nu) in s^-1 or Hz units


Equations for light

C = (lamda)(nu)

E = h (nu)

E = hc/(lamda)


Describe the quantum model

-Occurring to this model, orbitals are regions of probability for finding electrons
-orbitals (shells) are called principle quantum levels (principle energy levels), represented by the letter n (1 - infinity)
-The principle energy levels are comprised of sub units (s, p, d, f, etc)


Describe electron configuration

-Method of showing the distribution of electrons in terms or principal level, sub level and number of electrons present in the sub level
-The number of electrons present I'm the sublevel is restricted to being less than or equal to the maximum number it could hold


Order of filling

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 8s