Physics - Chapter 2

Structure of the Atom

Who is most often associated with the earliest atomic theory?

Leucippus

Who provided one of the most detailed and elaborate theories and is credited with expanding on and formalizing the earliest atomic theory?

Democritus of Abdera

Who discovered that atoms are solid, indivisible spheres?

John Dalton (1803)

Who organized known elements into a periodic table?

Dimitri Mendeleev

Who discovered electrons and created the “Plum Pudding” Model?

J.J. Thomson

What did Becquerel (1896) and Marie Curie discover (1898)?

Curie - radioactivity

Becquerel - radioactive rays

What did Ernest Rutherford do?

Conducted experiments with alpha particles - described a positively charged and very dense nucleus with tiny electrons orbiting around it in defined paths.

Proposed a new model of the atom that resembled a tiny version of our solar system.

True or False: The molecule is considered the basic building block of matter

False - the atom

What are the three fundamental particles?

Protons, Neutrons, Electrons

Describe the Bohr Model / theory

The atom is contained of 3 fundamental particles - protons, neutrons and electrons. The nucleus is central to the atom and is made up of protons and neutrons (called nucleons). The electrons orbit the nucleus in defined energy bands or shells.

Summarize the timeline of the atom

1803 - Dalton - Atoms exist

1897 - Thomson - Atoms contain electrons

1896 - Becquerel and 1898 - Curie - Atoms can emit radiation

1911 - Rutherford - Atoms have a nucleus and are mostly empty space

1913 - Bohr - Electrons orbit the nucleus in specific energy levels.

True or False: if an atom has an equal number of protons and electrons, it has no net charge

True

Describe Binding Energy

Keeps protons and neutrons bound together in the nucleus (holds the protons and neutrons together to form the nucleus of the atom)

is a measure of the amount of energy needed to split an atom;

Creates a strong attraction in the nucleus, overcoming the natural tendency for like charges to repel

What does electron binding energy depend on?

how close the electron is to the nucleus

how many protons are in the atom

The closer the electron is to the nucleus, the stronger the binding energy

What are the 2 types of atomic interactions in the x-ray tube that produce x-rays?

Characteristic - involve the removal of orbital electrons from atoms

Bremsstrahlung - involve attraction to the nucleus of the atom, and the penetrating strength (energy) of the x-ray photon produced depends on nuclear binding energy

An atom has defined energy levels, each at different distances from the nucleus. These energy levels are called

Electron Shells

Electrons orbit 3 dimensionally around the nucleus

What letter does the first electron shell begin with?

K

What is the formula to figure out the maximum number of electrons in each shell?

2(n)squared

(n) is the number of the shell (1, 2, 3, etc)

How many electrons can the first shell hold?

2

What is the maximum number of electrons the outermost shell can hold?

8

True or False: The more complex the atom, the greater the opportunity for a reaction

True

What does the atomic number refer to?

The number of protons it contains in its nucleus

What does the atomic mass number indicate?

The number of protons and neutrons an atom has in its nucleus

True or False: Each element is made up of one unique type of atom with an unchanging number of protons

True

True or False: Molecules are the simplest forms of substances that compose matter

False - elements

What is a molecule?

2 or more atoms bonded together

What is an isotoPe?

Elements whose atoms have the same number of protons but a different number of neutrons

What is an isotoNe

Elements whose atoms have the same number of neutrons, but different number of protons

What is an isobAr

Elements whose atoms have a different number of protons, but the same number of protons and neutrons —> the atomic mAss number is the same

What is an isomEr

Elements with the same number of protons and neutrons but different amounts of Energy within their nuclei

What is a compound?

A combination of elements bonded together

How is the periodic table organized?

7 periods arranged as rows (horizontal)

8 groups arranged as columns (vertical)

True or False: Atoms in each period have the same number of electrons in the outermost shell

False: each group (column)

Atoms in each PERIOD have the same number of electron shells; Atoms in each GROUP have the same number of electrons in the outermost shell

True or False: Atoms in period 6 are larger and more complex than in period 2

True

True or False: All compounds are molecules, but not all molecules are compounds

True

Describe an Ionic Bond

Based on the attraction of opposing charges,

One atom gives up an electron and one atom takes on an electron

The difference in electrical charge bonds them together

Describe a covalent bond

Based on two atoms sharing electrons that then orbit both nuclei

An outermost electron from one atom begins to orbit the nucleus of another adjacent atom in addition to its original nucleus

Similar to a figure 8 pattern