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Learn about the fascinating world of atoms and subatomic particles. Explore the concepts of mass, volume, energy, and the periodic table. Understand the role of protons, neutrons, and electrons in determining an atom's properties. Discover the importance of valence electrons and how they affect an atom's reactivity.
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Matter matters… • Matter • Made of atoms • Has volume • Has mass • Energy • No mass • No volume • Light/Sound/Heat
Just how small are we talking here? = 20,000,000,000,000,000,000,000 Atoms If you tried to count to 20 sextillion, it would take you about 100 trillion years- and that is only if you counted very, very fast!
Just how small are we talking here? An atom is the smallest unit into which an element can be divided and still retain the properties of that element.
Here’s the thing, though… The unit is called an amu, which stands for atomic mass unit. Atoms are actually so small that they themselves (and the stuff that makes them up) have their own mass units.
The tiny particles that make up atoms are called subatomic particles (literally “below atom” particles)
Protons Protons There are more than 114 different elements. Every element has a unique number of protons. Protons determine an element’s identity
Neutrons In nature, it is common to find atoms of the same element that have different numbers of neutrons. These are called isotopes.
Electrons Electrons can be found in the electron cloud which can also be referred to as energy levels. Neutral atoms have equal numbers of protons (+) and electrons (-). In one millionth of one second, electrons travel around the nucleus billions of times.
Electrons If an atom has unequal numbers of protons (+) and electrons (-), it is called an ion.
The electron cloud has the majority of the volume and almost none of the mass. The nucleus has almost no volume and has the majority of the mass. Mass and Volume of Atoms
Subatomic Particles and the Periodic Table that loved them… Elements are listed on the periodic table using their chemical symbols. Each chemical symbol is either a capital letter alone or one capital and one lowercase letter. H Ne Co
Subatomic Particles and the Periodic Table that loved them… What element is represented by the letters Na? What element is represented by the letter S? How many different elements are in this chemical formula: C6H12O6
The number of protons in an atom Atomic number Atomic mass The average mass of an atom of an element based on the natural abundance of that element’s isotopes.
Mass Number is the total number of protons and neutrons in a given atom. If it is not given to you, you calculate the mass number for an element by rounding the atomic mass to the nearest whole number.
Bohr Models Electrons are always spinning around the nucleus. They stay in general areas known as energy levels. Each level can only hold a limited number of electrons. first shell a maximum of 2 electrons second shell a maximum of 8 electrons third shell a maximum of 8 electrons
Bohr Models Electrons fill these energy levels from the lowest to the highest. The energy level must be completely full before moving on to the next level.
Bohr Models Bohr Models represent atoms by using circles to represent energy levels and dots or ‘x’s to show electrons. X Nitrogen N 7 X X 7P 7N X X 14 X X
Bohr Models Draw the Bohr model diagrams for the following elements: X X 8 17 O Cl a) b) X 35 X 16 X X X X X X 17P 18N X X X X X X X X 8P 8N X X X X X X X
Valence Electrons Electrons in the outermost shell are special- they are called valence electrons. Valence electrons determine how reactive an atom is (also called its reactivity). In order to be a stable atom, an atom must have a filled outer shell. *Special Note* outer shell does not automatically mean the third ring.
Valence Electrons In nature, atoms are stable. To achieve this stability, most atoms must either: • Gain electrons (4 or more valence e-) • Lose electrons (3 or less valence e-) The closer an atom is to stability, the more reactive it will be. *Special Note* You cannot gain or lose protons- this changes element identity!
Valence Electrons Overall charge of an atom is determined by counting total protons and electrons. Equal numbers = Neutral Atom More p+ than e- = Positive Ion More e- than p+ = Negative Ion *Special Note* You cannot gain or lose protons- this changes element identity!
