Matter & Atomic Structure Section 2.1 Part 1

Introduction What are all things made of? Matter – anything that takes up space and has mass. Matter is made up of chemical substances.

Chemical Substances Chemical Substance – matter that has definite composition. This composition is the same throughout. Chemical substances may be elements or compounds.

Elements Element – a pure substance. Cannot be broken down. Made of just one type of atom. Almost 120 known elements.

Elements

What is an atom? Atom: the smallest unit of matter that retains the identity of the substance First proposed by Democratus

Atomic Structure Atoms are composed of 2 regions: Nucleus: the center of the atom that contains the mass of the atom Electron cloud: region that surrounds the nucleus that contains most of the space in the atom Nucleus Electron Cloud

What’s in the Nucleus? The nucleus contains 2 of the 3 subatomic particles: Protons: positively charged subatomic particles Neutrons: neutrally charged subatomic particles

What’s in the Electron Cloud? The 3rd subatomic particle resides outside of the nucleus in the electron cloud Electron: the subatomic particle with a negative charge and relatively no mass

How do these particles interact? Protons and neutrons live compacted in the tiny positively charged nucleus accounting for most of the mass of the atom The negatively charged electrons are small and have a relatively small mass but occupy a large volume of space outside the nucleus

How do the subatomic particles balance each other? In an atom: The protons = the electrons If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

How do we know the number of subatomic particles in an atom? Atomic number: this number indicates the number of protons in an atom Ex: Hydrogen’s atomic number is 1 So hydrogen has 1 proton Ex: Carbon’s atomic number is 6 So carbon has 6 protons **The number of protons identifies the atom. Ex. 2 protons = He, 29 protons = Cu

How do we know the number of subatomic particles in an atom? Mass number: the number of protons and neutrons in the nucleus Ex: hydrogen can have a mass of 3. Since it has 1 proton it must have 2 neutrons # of neutrons = mass # - atomic # https://www.brainpop.com/science/matterandchemistry/atoms/

Determining the number of protons and neutrons Li has a mass number of 7 and an atomic number of 3 Protons = 3 (same as atomic #) Neutrons= 7-3 = 4 (mass # - atomic #) Ne has a mass number of 20 and an atomic number of 10 Protons = 10 Neutrons = 20 - 10= 10

What about the electrons? The electrons are equal to the number of protons So e- = p = atomic # Ex: He has a mass # of 4 and an atomic # of 2 p+ = 2 no = 2 e- = 2

Ti Particles 22 – Atomic Number 47.90 – Atomic Mass Protons = 22 Electrons = 22 Neutrons = 48-22 = 26 22 Ti Titanium 47.90

Determine the number of subatomic particles in the following: Cl has a mass # of 35 and an atomic # of 17 p+ = 17, no = 18, e- = 17 K has a mass # of 39 and an atomic # of 19 P+ = 19, no = 20 e- = 19

Isotopes Isotopes of an element have THE SAME atomic number but different MASS NUMBERS because they have a DIFFERENT number of neutrons Ex: Every atom of Oxygen has 8 protons but some oxygen have 8 neutrons and some have 9 neutrons depending upon the mass number. To distinguish different isotopes from one another we write them like this: element name-atomic mass Ex: oxygen-18, silicon-28, sulfur-34 https://www.brainpop.com/science/matterandchemistry/isotopes/

How exactly are the particles arranged? Bohr Model of the atom: Reviewers think this could lead to misconceptions! All of the protons and the neutrons The 3rd ring can hold up to 18 e- The 1st ring can hold up to 2 e- The 4th ring and any after can hold up to 32 e- The 2nd ring can hold up to 8 e-

What does carbon look like? Mass # = 12 atomic # = 6 p+ = 6 no = 6 e- = 6 6 p and 6 n live in the nucleus

Compounds Compound – a substance that consists of two or more elements. The smallest particles of a compound is called a molecule. Example: Water, H2O

Chemical Bonds Atoms stick together because of chemical bonds. Chemical bond – a force that holds molecules together. Three types of chemical bonds: Ionic Covalent Metallic

Ionic Bonds Ionic Bond - electrons are transferred from one atom to another. A compound formed through the transfer of electrons is called an ionic compound. Most ionic compounds are formed by the transfer of electrons from a metal to a nonmetal. Ex: Sodium Chloride (NaCl) = Table Salt.

Ions Ions – atoms that lose or gain electrons Positively or negatively charged Do not have the same number of protons and electrons Cations – lose electrons and become positively charged Anions – gain electrons and become negatively charged https://www.brainpop.com/science/matterandchemistry/ions/

Matter

Covalent Bonds Covalent bond - A bond based on the attraction between atoms that share electrons. Each covalent compound consists of only one kind of molecule, just as each element consists of only one kind of atom. Example: Water, glucose

Covalent Bonds When atoms share electrons, the positive nucleus of each atom is attracted to the negative electrons being shared. The pull between the positive and negative charges is the force that keeps the atoms joined.

Metallic Bonds Metallic bonds form when electrons are shared by metal ions. The sharing of an electron gives metals their characteristic properties. This is the sea of electrons.