Chem unit 2 (the atom, atomic structure, and light)

The atom, atomic structure, and light

What determines the chemical reactivity of an element?

electrons

What is emitted when an electron absorbs or emits energy? (light)

photon

How did the model of an atom change from Greek philosophers to Thomson and Rutherford?

From a dot to a positively charged dense nucleus with electrons orbiting it. Dense nucleus and empty space

Dalton’s Atomic Theory (4 parts)

1. all matter is made of indivisible atoms

2. all atoms of a given element are identical in mass and properties

3. compounds are combinations of 2+ different types of atoms

4. chemical reactions are a rearrangement of atoms

How big is an atom? Can you see it? Why?

Atoms are around 10^-10m in radius. You cannot see them because they are smaller than wavelengths of visible light.

Proton’s symbol, charge, location, approximate relative mass

p+, +1, nucleus, 1 amu

Neutron’s symbol, charge, location, approximate relative mass

n0, 0, nucleus, 1 amu

Electron’s symbol, charge, location, approximate relative mass

e-, -1, orbitals, 0 or 1/1840 amu

Define atomic number. Where can you find it?

It identifies an element by the number of protons. It’s in the top left corner of an element on the periodic table.

Define mass number. Where can you find it?

It tells the total number of protons and neutrons (added). It’s on the bottom of an element on the periodic table.

Define electromagnetic spectrum

The complete range of all frequencies/wavelengths of electromagnetic radiation

Types of energy on the electromagnetic spectrum

radio waves, microwaves, infrared, ultraviolet, x-rays, gamma rays

List from low to high all colors of the visible light spectrum.

lowest/highest energy

lowest/highest frequency

shortest/longest wavelength

low energy *red, orange, yellow, green, blue, indigo, violet* high energy

*ROY G BIV

red/violet

red/violet

violet/red

How to write nuclear symbol

mass number

element

atomic number

Define cation. How does it form?

A positively charged ion formed by an atom/molecule losing an electron

Define anion. How does it form?

A negatively charged ion formed by an atom/molecule gaining an electron

Molar mass calculations units are

grams/mole

What is an isotope? Name 2 ways that isotopes of the same element are different.

An isotope is the same element but with a different number of neutrons

1. number of neutrons

2. different mass number

How can there be 1000+ different atoms, but only about 118 different elements?

The rest are isotopes of the elements.

Explain how flame tests can be used to identify the metal present in an unknown compound

Metal ions emit their own colors. By comparing the observable flame colors, one can identify the metal.

Explain how an atom’s electron emits light energy when excited

When an electron absorbs energy it goes from ground state to excited state. The excited state is unstable so the electron emits light energy (photons) to stabilize itself and return to ground state.

What is the unit a.m.u.

Atomic Mass Unit is 1/12 of the mass of an unbound and neutral Carbon-12 atom in its ground state.

How is atomic mass calculated?

sum of (isotope mass * abundance) or weighted average of its natural isotopes

How do electrons absorb energy?

heat or collision

The smallest particle of an element that retains its identity in a chemical reaction is ______

atom

1. When a measurement is close to the actual or true value, it is called _.

2. When a series of measurements are repeatedly close to one another, it is called _

1. accurate

2. precise