Atom theory
All matter is composed of tiny particles called atoms.
All atoms of the same element are identical.
Atoms of different elements are different.
Atoms combine in simple, whole-number ratios to form compounds.
During chemical reactions atoms are rearranged to form new substances.
What is daltons atomic theory?
Name the subatomic particles in the nucleus of an atom
Protons and neutrons
What is radiant energy?
The energy that travels through space as electromagnetic waves moving at the speed of light.
What is the difference between the excited state and the group state?
“excited state" refers to an atom or molecule where one or more electrons have absorbed energy and moved to a higher energy level, making it less stable than its "ground state," while a "group state" is not a standard term in chemistry
What were atoms first called when they were discovered by Democritus?
Atomos
defined as one-twelfth the mass of a carbon-12 atom. This unit is used to express the relative masses of atoms and molecules.
Atomic Mass Unit (amu)
Who discovered the modern atomic structure and how?
Henry Moseley discovered that every element emitted x-rays of a characteristic wavelengths could be used to calculate an integer distinctive for each element. Moseley’s integers soon became known as atomic numbers of the elements.
A single unit or packet of a distinct amount of energy.
A quantum
What is the orbital notation of the outermost principal energy level of a sulfur atom in the ground state?
3s2 |⇅ |
3p4 |⇅ | ↑ | ↑ |
Who was the person that discovered the planetary model in 1914?
Neils Bohr
What was the difference between Democritus and daltons theories about a matter?
Democritus' ideas were purely philosophical and based on reasoning, while Dalton's theory was grounded in scientific experimentation
What are two ways to define isotopes?
(a) atoms of an element that contain the same number of protons but different number of neutrons.
(b) atoms with the same atomic number but a different mass number.
What is the quantum theory of radiation?
An electron absorbs a quantum of energy to jump up to a higher shell and then it releases a quantum of energy (light) when it falls to a lower shell.
Draw the Lewis dot digram for the following neutral atoms:
(a) nitrogen
(b) calcium
(c) oxygen
(d) boron
(e) potassium
(a) ••
• N •
•
(b) ••
C
(c) ••
• O :
•
(d) ••
• B
(e) •
K
What was found in the 1940’s?
The wave mechanical model
What did Rutherford discover?
He found out that most of an atom is empty space and contains a tiny, dense, positively charged core which he named the nucleus of the atom.
There are two isotopes of boron: boron-10 and boron-11.
(a) use the periodic table to find the atomic mass of boron.
(b) which isotope of boron do you suppose is more abundant in nature? Explain your answer in terms of the atomic mass.
(a) 10.81 u
(b) The atomic mass of boron (10.81 u) is closer to 11 than to 10. This indicates that boron-11 is the more abundant isotope in nature. Answer: Boron-11
Why did the electron shells eventually become known as principal energy levels?
They represent the principal quantum number (n) in the quantum mechanical model of the atom, which determines the energy level and average distance from the nucleus.
Identify the element with the following electron configurations. (200 Bonus label the electron configuration ground state or excited state.)
(a) 2-7
(b) 2-1-1
(c) 2-8
(d) 2-6-8
(e) 2-8-8-1
(f) 2-8-18-32-18-1
(a) Nitrogen (N), excited state; (b) Invalid; (c) Neon (Ne), ground state; (d) Sulfur (S), excited state; (e) Potassium (K), ground state; (f) Francium (Fr), ground state.
When was the hard partial model first discovered?
1808
Calculate the average atomic mass of chlorine given the information below:
Isotope l % Natural l Atomic
Symbol l Abundance l Mass (u) l
——————————————————————-
l 35Cl l 75.77% l 34.969 l
——————————————————————-
l 37Cl l 24.23% l 36.966 l
the average atomic mass of chlorine is approximately 35.45 u.
Calculate the average atomic mass of chlorine given the information below:
Isotope l % Natural l Atomic
Symbol l Abundance l Mass (u) l
——————————————————————-
l 32S l 95.03% l 31.972. l
——————————————————————-
l 33S l 00.75% l 32.971. l
——————————————————————-
l 34S l 04.22% l 33.968. l
32.068 u
Given the Lewis dot diagram:
••
• X :
••
Name 3 elements that could be elements X.
Oxygen (O), sulfur (S), and selenium (Se)
Write an electron configuration for the elements below in both ground state and the excited state. (Answers may vary for excited, and you may do it the long or short way).
(a) oxygen
(b) calcium
(c) helium
(d) phosphorus
(e) lead
(a) Ground state: 1s²2s²2p⁴. Excited state: 1s²2s²2p³3s¹ (or other variations).
(b) Ground state: 1s²2s²2p⁶3s²3p⁶4s². Excited state: 1s²2s²2p⁶3s²3p⁶3d¹4s¹ (or other variations).
(c) Ground state: 1s². Excited state: 1s¹2s¹ (or other variations).
(d) Ground state: 1s²2s²2p⁶3s²3p³. Excited state: 1s²2s²2p⁶3s¹3p⁴ (or other variations).
(e) Ground state: [Xe] 6s²4f¹⁴5d¹⁰6p². Excited state: [Xe] 6s¹4f¹⁴5d¹⁰6p²7s¹ (or other variations).
List all model of atom in order over time
The hard particle model - 1808
The plum pudding model - 1904
The nuclear model - 1911
The planetary model - 1914
The wave mechanical model - 1940