Chemistry Unit 2 CH. 4 & 5

Why did Rutherford's atomic model need to be replaced?

Could not explain the chemical properties of elements.

What does the quantum mechanical model determine about electrons in atoms?

Determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus.

How do two sub-levels of the same principal energy level differ from each other?

Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

How can electrons in an atom move from one energy level to another?

Enter an excited state and jump to the next one up- releasing energy seen as light coming down.

Explain why the actual electron configuration for some elements differ from those assigned using the aufbau principle.

Half-filled sublevels are not as table as filled sublevels, but they are more stable than other configurations.

How did dalton advance thee atomic philosophy proposed by democritus?

He turned it into a scientific theory

Why does one electron in a potassium atom go into the fourth energy level instead of squeezing into the third energy level along with the eight already there?

It will make it more stable in the fourth energy level.

Name two elements that have properties similar to those of the element Calcium (Ca)

Magnesium and Beryllium

What does the number represent in the isotope platinum-194?

Mass number ; 194Pt78

Atomic Orbital

a region of space in which there is a high probability of finding an electron

Atomic mass unit (amu)

a unit of mass that describes the mass of an atom or molecule

Write the electron configuration for each atom. How many unpaired electrons does each atom have? a. boron b. silicon

a. 1s22s22p1. 5 b. 1s22s22p63s23p1. 5.

Write the electron configuration for each atom. a. carbon b. argon c. nickel

a. 1s22s22p2 b. 1s22s22p63s23p6 c. 1s22s22p63s23p64s23d8

How many orbitals are in the following sublevels? a. 3p sublevel b. 2s sublevel c. 4p sublevel d. 3d sublevel e 4f sublevel

a. 2 b. 1 c. 2 d. 3. e. 4

List the number of protons, neutrons, and electrons in each pair of isotopes. a. 63Li, 73Li b. 4220Ca, 4420Ca c. 7834Se, 8034Se

a. 3 protons, 3 neutrons, 3 electrons and 3 protons, 4 neutrons, 3 electrons. b. 20 protons, 22 neutrons, 20 electrons and 20 protons, 24 neutrons, 20 electrons. c. 34 protons, 44 neutrons, 34 electrons and 34 protons, 46 neutrons, 34 electrons.

what experimental evidence led rutherford to conclude that an atom is mostly empty space?

because most of the particles weren't "deflected off" of the gold-foil in his experiment

pg. 116 #21 boron has 2 isotopes; boron-10 and boron-11. which is more abundant, given that the atomic mass of boron is 10.81

boron-11

Hund's Rule

electrons do not pair up until they have to

In your own words, state the main ideas of Dalton's atomic theory.

everything is made of atoms; chemical reactions happen when atoms are combined, seperated or rearanged but can never change from one atom to another

how does the rutherford model describe the structure of atoms?

having a positively charged, dense nucleus that is tiny compare to the atom as a whole

pg. 116 #22 there are 3 isotopes of silicon; they have mass numbers of 28, 29, and 30. The atomc mass of silicon is 28.086 amu. comment on the relative abundance of these three isotopes.

he average atomic mass is very close to 28 so that means the Si-28 isotope is the most abundant

how did democritus characterize atoms?

invisible and indistructable

what equation tells you how to calculate the number of neutrons in an atom?

multiply the mass of each isotope by its natural percent abundance and then add the products

what are the charges and relative masses of the 3 main subatomic particles?

proton: relative mass- 1 neutron: relative mass- 1 electron: relative mass- Very small (1/1836)

what are the 3 types of subatomic particles?

protons, neutrons, and electrons

what instrument can be used to observe individual atoms?

scanning tunneling microscoopes

Electron configuration

the arrangement of electrons in an atom

Quantum mechanical model

the modern description, primarily mathematical, of the behavior of electrons in atoms

describe the range of the radii of msot atoms in nanometeres?

the radii of most atoms fall within the range of 5x10 m to 2x10 m

Mass number

the sum of the number of neutrons and protons in an atomic nucleus

what distinguishes the atoms of one elements from the atom of another?

they contain different number of protons

how do the isotopes of a given element differ from one another?

they have different number of neutrons and different mass number

Quantum

The amount of energy required to move an electron from one energy level to another energy level

how is atomic mass calculated? numbers of protons, electrons, and neutrons?

The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance.

Atomic Mass

The average mass of all the isotopes of an element

Energy levels

The fixed energies of an electron

pg 117 #23 The element copper has naturally occurring isotopes with mass numbers of 63. and 64. The relative abundance and atomic masses are 69.2% for mass= 62.93 amu. claculate the average atomic mass of copper.

63.54 amu

pg. 117 #24 Calculate the atomic mass of bromine. the two isotopes of bromine have atomic masses and relative abundance of 78.92 amu (50.69%) and 80.92 amu (499.31%)

79.91 u

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

What makes the periodic table such a useful tool?

A periodic table allows you to easily compare the properties of one element (or a group of elements) to another element (or group of elements).

Electron

A subatomic particle that has a negative charge

Proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom

Neutron

A subatomic particle that has no charge and that is found in the nucleus of an atom

pg 112 #17 How many neutrons are in each atom?

A. 8 B. 16 C. 47 D. 35 E. 82

pg. 112 #18 Use table 4.2 to express the composition of each atom in shorthand form.

A. carbon-12: mass: 12 atomic # 6 C B. Fluorine-19: mass: 19 atomic # 9 F C. beryllium-9: mass: 9 atomic # 4 Be

Pauli exclusion principle

An atomic orbital may describe at most two electrons, each with opposite spin direction

What was the basic new proposal in the Bohr model of the atom?

An electron is found only in specific circular paths, or orbits, around the nucleus.

Aufbau principle

An electron occupies the lowest-energy orbital that can receive it

Isotopes

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

What are the three rules for writing the electron configuration of elements?

Aufbau principle, pauli exclusion principle and hund's

Use figure 5.7 to arrange the following sublevels in order of decreasing energy.

3d, 3p, 2p, 4s, 3s.

Atom

Basic unit of matter

The atomic masses of elements are generally not whole numbers. Explain why

Because the elements have different isotopes. The atomic mass is the average of all the isotopes of that element that exist.

according to dalton's theory, is it possible to convert atoms of one element into atoms of another? explain.

No - they may separate, join, or rearrange - but atoms of one element are never changed into atoms of another element

Atomic Number

Number of protons

compare rutheford's expected outcome of the gold-foil experiment with the actual outcome.

Rutherford thought "Thomson MOdel" was correct and the initial results supported this interoperation. took him 2 years

The energies of electrons are said to be quarantined. Explain what this means.

They can change with an increase of energy or process of losing energy.

describe thomson's and millikan's contributions to the atomic theory.

Thomson: first person to suggest the theory of the atom containing positive and negative particles and demonstrated the latter which are called "electrons" Millikan: discovered that the weight of an electron is 1840 times smaller than a hydrogen atom(atomic mass of 1)

How did rutherford's model of the atom differ from Thompson's

Thomson: thought the protons and electrons were both distributed as a mixture with in a sphere Rutherford: thought only protons formed a spherical core or nucleus and the electrons were outside the nucleus, in the orbit around it