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This page is still under construction [no images.] For the complete notes get the Word document version of How to “Build” an Atom Of an Element Part 1
How to "Build" an Atom of an Element [part 1] Using the Periodic Table of the Elements 1. The Atomic Number gives the number of protons [+].Since this is the number of protons, the Atomic Number is always a whole number!
Protons have a positive charge [+1]. Protons are massive ["heavy"] and so are found in the center, or nucleus, of the atom. Protons have a mass of 1 [in atomic mass units, or AMU.] Atoms have an overall [total] electrical charge of zero [no charge, neutral] So the number of protons [+] is equal to the number of electrons [-] How do you find the number of electrons on an element’s "box" on the Periodic Table?
2. The Atomic Number also gives the number of electrons [-].
Electrons are not massive, so we ignore the mass of electrons in 8th Grade. Electrons "orbit" [or circle around] the nucleus of the atom. [So we picture electrons with a circle around the nucleus, similar to how we picture the earth orbiting the sun.] This "orbit" is called an Energy Level. 3. Neutrons have no charge [zero charge, are neutral.] Neutrons are massive, so are found in the nucleus. Neutrons [for 8th Grade science] have a mass of 1 AMU. So the nucleus can contain two types of sub-atomic particles, protons and neutrons. For 8th Grade, all the mass of an atom is in the nucleus. We know that protons make up some of the mass of an atom, because all atoms have at least 1 proton. If the mass of an atom is greater than its number of protons, any "extra" mass must be due to neutrons. So to find the number of neutrons, we need more information about the atom. We need the Atomic Mass Number, This number is always given as a decimal *, not a whole number, so we won’t get it confused with the Atomic Number. We round it to the nearest whole number to find the number of neutrons. [So for Helium above, we round to 4, since we couldn’t have .003 of a neutron. We either have one, or we don’t!] The total mass of He we say is 4. We know that "all" the mass is in the nucleus, in the form of protons and neutrons. How many protons are in HE? Since He "weighs" more than that [4], how many neutrons will we need to add to those protons to give He it’s total atomic mass of 4? Here’s how we draw Helium: Notice the total number of nuclear particles [nucleons] is equal to the Mass Number [rounded to the nearest whole number], which for Helium is 4. Why are there 2 electrons in this picture? What is the total charge for this atom? What is its total "weight"? [ignore the electrons!] *because it is an average. How to "Build" an Atom of an Element
Check your work! 1. Does your picture have the same number of protons in its nucleus as the Atomic Number for your element? 2. Are the protons labeled with a positive charge? [ +]3. Is the overall charge on your atom zero? [Do you have the same number of electrons as protons] 4. Are the electrons shown orbiting around the nucleus? 5. Are the electrons labeled with a negative charge? [ -]6. What is the Mass Number of the element when rounded? 7. Did you add the correct number of neutrons to have the same number of particles in the nucleus as does the rounded Atomic Mass Number? 8. Are your neutrons labeled? For Part 2 of "How to Build an Atom" 9. Is the 1st Energy Level Filled with 2 e- [except for H] ? 10. Are [the remainder of] your electrons on their proper Energy Levels? [2nd Energy Level fills with 8 e-]
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