Aca Deca 2022-23 Science

-Electrically neutral
-Same number of protons and electrons
-number of protons defines its element

Atom

-Electrically charged
-Different number of protons and electrons
-May contain one or more atoms

Ion

Atoms

smallest distinct particles that make up matter

What does the internal structure of an atom determine in an element?

The element's chemical behavior

What is the structure of an atom?

There is a nucleus made up of protons(+) and neutrons(no charge) surrounded by a cloud or ring of electrons(-). In a neutral charged atom, there is one proton for every electron.

How are ions formed?

atoms can lose or gain one or more electrons to form, respectively, positive or negative ions.

Mass spectrometers

-instrument that determines the relative mass of a single atom
-are able to separate and measure atoms and compounds because moving charged species (ions) of different mass (and energy) are affected differently by magnetic or electric fields

Three basic components of a mass spectrometer

1. An ion source where compounds or atoms are converted into (usually positive) ions;

2. A mass analyzer where the ions are accelerated in magnetic fields and take different pathways;

3. A detector that measures the number of ions of each mass that are present.

Mass spectrometer used in airports

a straight pathway used with a cycling magnetic field

Which Greek philosopher proposed the concept of atomism?

Leucippus

John Dalton

English chemist, meteorologist, and physicist who developed the atomic theory of matter in the 19th century

Dalton's Law of Partial Pressures

states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture, (Ptotal = Pa + Pb)

Law of Conservation of Mass

the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes, mass of reactants is equal to the mass of the products

Who proposed the law of conservation of mass?

Antoine Lavoisier (1789)

law of definite proportions

a substance is always composed of the same proportion of each element.

Who proposed the law of definite proportions?

Joseph Proust (1799)

Dalton's Law of Multiple Proportions

if two elements combine to form more than one compound, the ratios of their masses are whole numbers that are determined by the atomic weights of the elements involved.

When did Dalton publish "A New System of Chemical Philosophy"

1808

A New System of Chemical Philosophy

Published in 1808 by John Dalton; included Dalton's basic atomic principles

Dalton's major conclusions on atomic behavior

-All matter is composed of very small, indivisible particles called atoms.
-Atoms of the same element have the same properties (size, mass, etc.) while atoms of different elements will have different properties (e.g., hydrogen has different properties than lead).
-Atoms cannot be divided any further and cannot be created or destroyed.
-Atoms of different elements can combine in whole-number ratios to form compounds.
-Chemical reactions can cause atoms to combine, separate, and rearrange.

Which element does not contain any neutrons?

Hydrogen

What is the atomic number?

the number of protons in an atom

How do you find the mass number

the number of protons plus the number of neutrons

in (A/Z)X, What does the A represent?

The Mass Number

in (A/Z)X, What does the X represent?

The Element

in (A/Z)X, What does the Z represent?

The Atomic Number

What never changes in an element?

number of protons (atomic number)

What is an isotope?

Atoms of the same element that have different numbers of neutrons

What is a nuclide?

Any arrangement of protons and/or neutrons forming a nucleus

What indicates the number of neutrons

The mass number minus the number of protons will indicate the number of neutrons

radioactive atoms

atoms that are unstable and decay over time

Deuterium

-An isotope of hydrogen with one proton and one neutron in the nucleus having an atomic weight of 2.014
-all forms of compounds containing hydrogen, such as water, contain small amounts of deuterium

atoms of deuterium per 6500 hydrogen atoms

1 atom of deuterium for every 6,500 atoms of hydrogen.

What is deuterium used for?

deuterium can be used as a "tracer" to find out how chemical reactions of hydrogen occur.

What is the most common nuclide used in fusion reactors?

Deuterium

What is the half-life of carbon-14?

5730 years

Why is carbon-14 radioactive?

Number of neutrons is increased to 8

*Unequal balance of protons and neutrons* is what makes something radioactive
*It is unstable

What is carbon-14 useful for

the dating of materials containing carbon, such as wood or bones.

What is the half life of cobalt

5.3 years

What do you need to know to calculate the weighted average atomic mass of an element?

You need to know the mass and abundance of each isotope

How do you determine an electrons energy levels in an atom?

Exciting the electron;
-heated strongly
-raised to a higher energy level

What is it called when the absorbed or emitted photons are examined for their energy?

absorption spectrum or emission spectrum

Who established the Bohr model of an atom

Danish physicist Niels Bohr

What is the quantum mechanical model?

-electrons are not at exact distances or fixed locations and do not rotate in orbits.
-It determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus

The Davisson-Germer experiment showed...

The wave properties of electrons where electrons scattered at preferred angles from a nickel crystal

What is an orbital?

A region of space around the nucleus where an electron is likely to be found.

What is the periodic table?

an arrangement of stable atoms according to their electronic orbital structure.

How are elements arranged on the periodic table?

by increasing atomic number

What are the horizontal rows on the periodic table called?

periods

What are the vertical columns on the periodic table called?

groups

How many "A" groups are there on the periodic table

8

How many "B" groups are there on the periodic table

10

What are the "A" groups on the periodic table?

The main groups,
-elements within the A groups all have the same amount of valence electrons

What does the position of an element on the periodic table allow one to predict?

The element's properties

Electronegativity

a measure of one atom's attraction of electrons from an adjacent atom to which it is chemically bonded.

Who devised the method of arriving at a single numerical value for relative electronegativity? What is the method referred to as?

Linus Pauling, Pauling electronegativity

What is the atomic radius?

a measure of atomic size

What does the atomic radius do?

decrease from left to right across a period and increases down a group of the period table

Define ionization energy

the energy required to entirely remove an outer electron from an atom

the term applied to an atom as a measure of the fact that most neutral atoms still exhibit a small attraction for an electron

Electron affinity

What is an ionic bond?

A chemical bond that's formed when an atom transfers and electron to another Atom

What is a covalent bond?

A chemical bond formed when two or atoms share electrons.

What is a dipole moment?

a measure of the separation of two opposite electrical charges

When do dipole moments occur?

in molecules that have a positive end and a negative end and provide a measure of the molecule's polarity

A molecule is a...

group of atoms held together in a constant ratio by strong covalent bonds

What is a "cluster" of elements called

a compound

Electrostatic forces

- force of attraction between opposite charges, AND
- force of repulsion between the same charges

intERmolecular forces

exist BETWEEN molecules

intRAmolecular forces

bond atoms together WITHIN a molecule

What is metallic bonding?

the chemical bonding that results from the attraction between metal atoms and the surrounding "sea" of electrons

When more than one element is present in a metal, the metal is call a/an...

alloy

Brass is made from

copper and zinc

These are classified as ionic, covalent, or metallic bonds.

Intramolecular Forces

Intermolecular forces are ________ than intramolecular forces

weaker forces of attraction

What are intermolecular forces responsible for

causing a clustering effect in liquids and solids

the name given to an intermolecular force first recognized by Johannes van der Waals

Van der Waals force

Molecules are said to be ___________ if a permanent distance can be measured between the center of positive charge and the center of negative charge

polar molecules

What is another name for a polar molecule

dipole moment

Lavoisier discovered that air was composed primarily of

O2 and N2

the process when electron orbitals like s and p mix together to form new orbitals such as sp

hybridization

What is the ratio of hydrogen to fluorine to form the compound HF

1:19

amu stands for

atomic mass unit

London dispersion forces

the intermolecular attraction resulting from the uneven distribution of electrons and the creation of temporary dipoles

london dispersion forces were discovered by

Fritz London

Cavendish referred to hydrogen as

"flammable air"

Antoine Lavoisier named the "flammable air"

hydrogène.

What did Cavendish confirm in 1781?

burning hydrogen produced water

Who took note that flammable gas was produced when iron was dissolved in acid

Robert Boyle

VSEPR stands for

Valence Shell Electron Pair Repulsion

On august 27, 1783, Roberts and Charles launched...

the first hydrogen-powered balloon

The flight of the first hydrogen-powered balloon lasted about

45 minutes

What were hydrogen balloons referred to after Charles could no longer ride in the balloons

Charlière

Charles' Law

V1/T1=V2/T2

What does Charles' Law state

As temperature increases, volume increases and as temperature decreases, volume decreases

KMT

kinetic molecular theory

Avogadro's Law

V1/n1=V2/n2

What does Avogadro's Law state?

no matter the nature of the gas, at a given temperature, pressure, and volume, there would be the same number of molecules

what is the formula of force

Force = mu^2/ℓ

what is a mole

the standard international base unit used to measure the amount of a substance

Avogadro's number

6.02 x 10^23