Understanding Atoms, Elements, and Compounds

1. Matter • Everything around you is matter • Matter is anything has mass and volume • Mass is the amount of matter in a substance • Volume is the amount of space the substance occupies. • All substances are types of matter

2. Atoms and Elements • Atoms are the basic building blocks of all matter. • An atom is the smallest particle of matter. • Each kind of atom is an element. • Atoms are elements

3. Atoms and Elements • An element is a pure substance that cannot be broken down into simpler substances. • Scientists from all over the world have discovered 117 confirmed elements. • 90 of these elements are found in nature

4. Atoms and Elements • The remaining elements are synthetic or made by humans. *

5. Atoms and Elements • An atom is the smallest particle of an element that has all the particles of that element. • Each type of element is made up of atoms that differ from those of every other element. • Elements are found in chemical groups/families and Periods on the Periodic Table

6. Atoms and Their Parts • The center of the atom is called the nucleus. • The nucleus of most atoms is made up of two kinds of particles: Protons positive (+) charge and Neutrons (no charge….zero charge). • The nucleus of the atom carries the most mass and is positively charged

7. Atoms and Their Parts • Protons have a positive charge(+). • Neutrons have no charge(0). • Electrons are subatomic particles that move around in an outside the nucleus of the atom. • Electrons carry a negative (-) charge

8. The Element Square

9. Parts of the Element Square • The properties or characteristics of an element are determined by the structure of its atom. • The main feature used to distinguish the atoms of different kinds of elements is atomic number • Atomic number describes the number of protons in the nucleus of an atom. • No two elements have the same atomic number

10. Elements and Subatomic Particles • The number of protons (the atomic number) in the nucleus of an atom is unique for each element. • Atomic numbers increase by 1 as you go from left to right on the periodic table • The number of protons in the atom is equal to the number of electrons.

11. Elements and Subatomic Particles • As a result of this arrangement, each positive charge in the nucleus is balanced by a negative charge in the electrons surrounding the nucleus. • The atom as a whole is electrically neutral and has no overall charge. * Atoms have mass-most of the mass is in the nucleus

12. Elements and Subatomic Particles • The atomic mass of an atom is equal to the number of protons plusthe number of neutrons in the atom’s nucleus. • Electrons are found outside the nucleus, and are so small that they contribute almost no mass to an atom

13. Elements and Subatomic Particles • Electrons are found in the cloud on what is known as the outer shell, orbital and sometimes it is referred to as the atom’s valence, bonding shell • Electrons have a (-1) charge ….very, very light in mass

14. Elements and Subatomic Particles • Atomic mass is determined by counting only the number of protons and neutrons in an atom of an element. • Calculate the neutron number by subtracting the atomic number from the mass/weight number of the atom.

15. Another Look: The Element Square

16. Practice Time!Complete the Element Squares! 4 B P 22 K Neon

17. Classifying Matter • Pure Substances • elements/atoms • compounds 2. Mixtures • homogeneous • heterogeneous

18. Elements form Compounds • Elements and compounds are examples of pure substances • A pure substance has a single, definite composition, and can not be considered a mixture. • No matter how small the sample, properties and chemical make-up are the same throughout in a pure substances.

19. Pure Substances are Atoms, Elements and Compounds • We refer to atoms/elements and compounds as pure substances because they cannot be separated easily into the parts that make them up • A compound is a pure substance that forms when two or more different kinds of elements join chemically. Ex: Water is made of hydrogen AND oxygen • The atoms of the elements that make up a compound bond to one another chemically.

20. Compounds • Compounds are very strongly and cannot be broken apart easily because of their chemical bonds. • Bonding takes place when the elements making up a compound join by sharing or transferring electrons in the outer most valence shell of the atom. • The elements that form a compound do not keep their original, individual properties.

21. Molecules • A molecules is the smallest unit of a compound that has all the properties of the compound. • Molecules can consist of two or more of the same elements….O₂, and N₂ are example • All compounds are considered molecules, but not all molecules are compound…why is this true?

22. Chemical Formulas • A chemical formula uses chemical symbols and subscripts to identify the number and types of atoms of each element that make up a molecule of a compound. Check out these common formulas for compounds we use daily! Ammonia is used in hair dye!

23. Subscripts • A subscript is a small number written to the right and slightly below a chemical symbol to tell the number of atoms of that element in the substance. • All compounds have a definite composition. • Each compound has its own chemical formula.

24. Mixtures • Elements can combine in different ways to form either compounds or mixtures. • A mixture forms when two or more substances combine without joining together chemically. • The substances that form a mixture are not bonded together chemically.

25. Mixtures • Because they do not combine chemically, the parts of a mixture retain their individual identities and properties. • A mixture that is unevenly mixed is called a heterogeneous mixture. Ex: trail mix and soil • A mixture that is mixed evenly throughout the substance is called a homogeneous mixture. Ex: ocean water

26. Mixtures • Common Mixtures: • Raisin Bran Cereal-Heterogeneous Mixture • Ocean water- Homogeneous Mixture

27. A stinker thinker….. Is air a mixture or compound? Answer: It is a mixture of compounds!