ATOMS

What is an Atom? Glance at the painting to the right and you see people enjoying an afternoon in the park. Now look closely at the circled detail of the painting. There you’ll discover that the artist used thousands of small spots of color to create these images of people and the park. Are you surprised that such a rich painting can be created from lots of small spots? Matter is like that, too. The properties of matter that you can observe result from the properties of tiny objects that you cannot see.

What is an Atom? Atoms are the tiny objects that make up all matter. Definition: The basic particle from which all elements are made. Atoms are building blocks that combine to form larger structures.

Why is it useful to model atoms? Since atoms are too small to see, scientists use models to help us visualize the structure and properties of the atom.

What three particles make up the atom? Protons Neutrons Electrons

Nucleus The central core of an atom containing protons and usually neutrons. Nucleus

Proton Proton A small, positively charged particle in the nucleus of the atom.

Neutron Neutron A small particle in the nucleus of the atom, with no electrical charge.

Electron Electrons A tiny negatively charged particle that moves around the nucleus of an atom.

Atoms are neutral: P = E In an atom, the number of protons equals the number of electrons. As a result, the positive charge from the proton equals the negative charge from the electrons. The charges balance, making the atom neutral (has no charge).

Is there a rule about neutrons? In an atom, the number of neutrons are equal to or greater than the number of protons. Atoms with an atom can vary.

What three particles make up the atom? Protons Neutrons Electrons

Atoms and Elements An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing a single proton and a single electron.

Atoms and Elements Oxygen Neon An element can be identified by the number of protons in the nucleus of its atoms. If you change the number of protons an atom has, you change the type of element it is.

What part of the atom determines what type of element it is? The number of protons in the nucleus of the atom determines the type of element it is. This atom has 3 protons.

How many protons, neutrons and electrons does this atom have? Red – Proton Blue – Neutron Gray – Electron Answer: 3 Protons, 4 Neutrons, 3 Electrons.

Which element is this? This atom has 3 protons. Look on the Periodic Table of Elements on pages 84/85 in your text (next slide). Find the Element that has the Atomic Number 3 (above it). What is this element?

What is this Element? LITHIUM

What three particles make up the atom? Protons Neutrons Electrons

An atom has the same number of which two particles? An atom has the same number of protons and electrons.

How are elements identified in terms of their atoms? 8 Protons identifies this Atom as an Oxygen Element How are elements identified in terms of their atoms? Atoms are identified by the number of protons in their nucleus.

Why is it useful to model atoms? Since atoms are too small to see, scientists use models to help us visualize the structure and properties of the atom.

Atomic Number, Mass Numbers and Isotopes: How Atoms are Identified

Which element is shown in the Bohr atomic model below?

Carbon Atom

The Periodic Table of Elements has one square for each element. Atomic Number The Periodic Table of Elements has one square for each element. Each square includes the element’s atomic number, chemical symbol, name and atomic mass. Chemical Symbol Chemical Name Mass Number

Atomic Number Mass Numbers Atomic Number – is the number of protons in the nucleus of the atom. Mass Number – is the sum of the protons and neutrons in the nucleus of the atom. Chemical Symbol Chemical Name Mass Number

Compare and contrast the atoms below.

Isotopes Although all atoms of an element have the same number of protons, their number of neutrons can vary. Isotopes are atoms with the same number of protons and a different number of neutrons.

The language of chemistry: Isotopes Chemists can indicate an Isotope in two different ways. Carbon-12, Carbon-13 or Carbon-14 Symbol and Atomic Mass/Atomic Number How many neutrons are in the Carbon atoms shown to the right? 6 in Carbon 12 and 8 in Carbon 14