Unit 2/B: Chemical Interactions Chapter 5: Atomic Structure and the Periodic Table Chapter 6: Chemical Bonds and Compounds Chapter 7: Chemical Reactions Chapter 8: Solutions Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Chapter 5: Atomic Structure and the Periodic Table 5.1 Atoms are the smallest form of elements 5.2 Elements make up the periodic table 5.3 The periodic table is a map of the elements A substance’s atomic structure determines its physical and chemical properties Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.1 Atoms are the smallest form of elements Before, you learned: All matter is made of atoms Elements are the simplest substances Now, you will learn: Where atoms are found and how they are named About the structure of atoms How ions are formed from atoms Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

All matter is made of atoms Substances vary - How many different substances can there be? 2400 years ago – Greek philosophers thought there were four basic substances – air, water, fire, and earth Today – chemists know of about 100 basic substances, call elements, that account for everything we see and touch Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atoms in Earth’s Crust and Living Things Atoms of the element hydrogen account for about 90% of the total mass of the universe Hydrogen makes up only about 1% of the Earth’s crust – mostly in the form of water % by mass Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Names and Symbols of Elements Name Origin Examples: – Magnesium from the region in Greece, Magnesia – Lithium from Greek word lithos, “stone” – Neptunium named after planet Neptune – Einsteinium and Fermium named after scientists Albert Einstein and Enrico Fermi Elements have a name and symbol – Hydrogen: H – Sulfer: S – Carbon: C – Aluminum: Al – Cadmium: Cd – Lead: Pb – Iron: Fe – Gold: Au (from aurum, Gold in Latin) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Each element is made of a different atom Early 1800’s: British scientist John Dalton: – each element is made of tiny particles called atoms – All atoms of a particular element are identical, but are different from atoms of all other elements Ex: the atoms of silver are different from an atoms of iron – Atoms cannot be divided into anything simpler Not exactly true… Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

The Structure of an Atom Atoms contain charged particles – either positive or negative – Positives repel positives – Negatives repel negatives – Positive and negative attract Atoms – three types of particles: – Protons – positively charged – Neutron – uncharged – Electron – negatively charged Protons and neutrons are – found in the nucleus of an atom – Are of similar mass Electrons – move around the outside of the nucleus – Have a much smaller mass than protons or neutrons Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

The Structure of an Atoms Atoms are about m in diameter! – Millions of atoms are in the period at the end of a sentence – The electron cloud is actually 10,000 times the diameter of the nucleus! But…electrons are bout 2000 times smaller than the protons or neutrons Can never determine the exact location of an electron – always moving around Negative attraction to the positive keeps electrons close to the nucleus, but away from each other – No electrical charge if # protons = # electrons Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Numbers and Mass Numbers All atoms are composed of the same particles… – Different numbers of protons in the nucleus Atomic number = # protons in the nucleus Atomic mass number = # protons + # neutrons – Same elements have same # protons but not always the same # neutrons, so may have different atomic masses – Ex: Chlorine atoms have 17 protons, some have 18 neutrons, some have 20 neutrons = Chlorine isotopes – Isotopes: atoms of the same element that have a different number of neutrons Chlorine-35, Chlorine-37 – # protons? # neutrons? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atoms form ions If # protons = # electrons  no electrical charge Ion: formed when an atom loses or gains one or more electrons – What if an atoms loses a proton? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Formation of Positive Ions If the atoms loses one electron, the charges are no longer balanced: one more proton than electrons Size is different: fewer electrons, less repulsion Lose one electron: X +, lose two electrons: X 2+ Ex: Na +, Ca 2+ If the atoms loses one electron, the charges are no longer balanced: one more proton than electrons Size is different: fewer electrons, less repulsion Lose one electron: X +, lose two electrons: X 2+ Ex: Na +, Ca 2+ Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Formation of Negative Ions Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties If the atoms gain one electron, the charges are no longer balanced: one less proton than electrons Size is different: more electrons, more repulsion Gain one electron: X -, gain two electrons: X 2- Ex: Cl -, O 2- If the atoms gain one electron, the charges are no longer balanced: one less proton than electrons Size is different: more electrons, more repulsion Gain one electron: X -, gain two electrons: X 2- Ex: Cl -, O 2-