Elements and Compounds Atomic Theory Elements Compounds and

  • Slides: 20
Download presentation
Elements and Compounds Atomic Theory

Elements and Compounds Atomic Theory

Elements, Compounds, and Mixtures Matter can be broadly classified into 3 types ◦ Mixtures

Elements, Compounds, and Mixtures Matter can be broadly classified into 3 types ◦ Mixtures ◦ Compounds ◦ Elements

How do Different kinds of molecules differ? Nearly all matter (molecules) we encounter in

How do Different kinds of molecules differ? Nearly all matter (molecules) we encounter in life is a mixture of substances. Mixture = blend of 2 or more substances ◦ Air = mixture of gases ◦ Tap water = minerals and gases

What happens when a mixture is separated? When components of mixture are separated, they

What happens when a mixture is separated? When components of mixture are separated, they are separated into pure substances. Pure substance =constant properties and constant composition ◦ Example: Salt water = salt + water

Can pure substances be divided into different categories? Pure substances can be divided into

Can pure substances be divided into different categories? Pure substances can be divided into 2 categories: compound or element

Elements and Compounds Element = simplest type of matter with unique physical and chemical

Elements and Compounds Element = simplest type of matter with unique physical and chemical properties. ◦ Element consists of only one kind of atom Compound =type of matter composed of two or more different elements that are chemically bound together.

Defining the Atom An atom is the smallest particle of an element that retains

Defining the Atom An atom is the smallest particle of an element that retains its identity in a chemical reaction.

Dalton’s Atomic Theory 1. All elements are composed of tiny particles called atoms. 2.

Dalton’s Atomic Theory 1. All elements are composed of tiny particles called atoms. 2. Atoms of the same element are identical. 3. Atoms of different elements can physically mix in simple whole number ratios to form compounds. 4. Chemical reactions occur when atoms are separated, joined, or rearranged.

How do we represent atoms? We draw circle pictures!!! Dalton drew circle pictures to

How do we represent atoms? We draw circle pictures!!! Dalton drew circle pictures to represent each kind of atom. Element A Element B Mixture of A & B Compound Another of A & B Compound of A & B

Atom & Molecule Cartoons What’s in the box? ◦ Individual atoms, or molecules? ◦

Atom & Molecule Cartoons What’s in the box? ◦ Individual atoms, or molecules? ◦ Substance (pure) or mixture? ◦ Compound, element, or both? 10

Atom & Molecule Cartoons What’s in the box? ◦ Individual atoms, or molecules? ◦

Atom & Molecule Cartoons What’s in the box? ◦ Individual atoms, or molecules? ◦ Substance (pure) or mixture? ◦ Compound, element, or both? 11

Atom & Molecule Cartoons What’s in the box? ◦ Individual atoms, or molecules? ◦

Atom & Molecule Cartoons What’s in the box? ◦ Individual atoms, or molecules? ◦ Substance (pure) or mixture? ◦ Compound, element? 12

The Nuclear Model of the Atom Rutherford proposed: ◦ The atom’s mass is concentrated

The Nuclear Model of the Atom Rutherford proposed: ◦ The atom’s mass is concentrated in a tiny positive nucleus ◦ Lightweight negative electrons circle the nucleus as planets orbit the sun ◦ Most of the atom is empty space 13

Atomic Composition Atoms are made up of subatomic particles: Particle Charge Location Mass Electron

Atomic Composition Atoms are made up of subatomic particles: Particle Charge Location Mass Electron (e-) Negative (-) Outside nucleus 9. 109 x 10– 28 g Proton (p+) Positive (+) Inside nucleus 1. 673 x 10– 24 g Neutron (n 0) No charge Inside nucleus 1. 675 x 10– 24 g

Structure of Atom 1. Most of the volume in an atom is occupied by

Structure of Atom 1. Most of the volume in an atom is occupied by electrons. 2. The nucleus is the central core of an atom and it is composed of protons and neutrons.

Distinguishing Between Atoms • The number of protons present in an atom determines which

Distinguishing Between Atoms • The number of protons present in an atom determines which atom you have. Protons = atomic number. • The mass # of an atom is determined by the number of protons and neutrons. Mass # = protons + neutrons Neutrons = mass – protons • Not all elements are the same. Isotopes =same element with a different # of neutrons This is called the weighted mass average. • This system of mass based on the mass of Carbon-12.

Atomic composition mass number, A protons + neutrons atomic number, Z protons 23 1+

Atomic composition mass number, A protons + neutrons atomic number, Z protons 23 1+ Na 11 ion charge protons – electrons Atomic number is found on the periodic table Mass number is NOT found on the periodic table An atom may gain/lose electrons to form an ion If no charge is shown, the charge is zero (a neutral atom) 17

Let’s practice Symbol 12 Protons Neutrons Electrons Atomic # C 21 Mass #

Let’s practice Symbol 12 Protons Neutrons Electrons Atomic # C 21 Mass #

Isotopes l Atoms with the same number of protons but different numbers of neutrons

Isotopes l Atoms with the same number of protons but different numbers of neutrons are isotopes of the same element 6 Li and 7 Li are isotopes of lithium l Both are the element lithium l 6 Li has 3 protons, 3 neutrons l 7 Li has 3 protons, 4 neutrons Their chemical behaviors are identical

Let’s Practice Oxygen has three naturally-occurring isotopes, with 8, 9, and 10 neutrons. Write

Let’s Practice Oxygen has three naturally-occurring isotopes, with 8, 9, and 10 neutrons. Write the symbols for each of the isotopes.