The atomic number of an atom is always equal to the total number of A. Neutrons in the nucleus B. Protons in the nucleus C. Neutrons plus protons in the atom D. Protons plus electrons in the atom 2. An atom of an element contains 20 protons, 20 neutrons, and 20 electrons. This element is A. An alkali metal B. An alkaline earth metal.
The number of neutrons in an atom is the number of protons subtracted from the mass number. For instance Carbon weighs 12.01 amus and has 4 Protons, therefore it has 8 neutrons because protons. Get an answer for 'Why is the sum of the number of protons and neutrons in an atom not equal to that atom's atomic weight?' And find homework help for other Science questions at eNotes. The number of neutrons in an atom is equal to the number of protons. All atoms of the same element have the same number of electrons and protons, but may have.
Below is a quick explanation of all the items on the fact sheets
Basic Information
Symbol- Each element is assigned a chemical symbol. This symbol usually originates from its name or its Latin name. For example, silicon has a chemical symbol 'Si'. Each element's symbol is composed of a capital letter followed by one or two lowercase letters.
Atomic Number- Each atom has an atomic number. This atomic number is equal to the number of protons in the nucleus of that particular atom. For example, the element cobalt (Co) has an atomic number of 27. This atomic number is also the number of protons in the atom. Therefore, Co has 27 protons.
Mass- The mass of an atom, expressed in atomic mass units (AMU), is roughly equal to the number of protons plus the number of neutrons. This is because both the protons and the neutrons in an atom have a relatively equal mass. The mass of an electron is so insignificant that it is not represented in the atomic mass. Since not all atoms have only one isotope1, the atomic mass is the average of all isotopes, once abundance is computed. For example, if you took a container of the element hydrogen (H), 99.984% of it would be H-1, 0.0156% of it would be H-2, and 0% of the hydrogen would be H-3. Since H-1 has one proton and no neutrons, its mass is 1. Because H-2 has one proton and one neutron, its mass is 2. Therefore, when you compute the percentages of the isotopes of H in any container, you find that the atomic mass of H is actually 1.0079. If the atomic mass of a particular element is shown in parentheses, such as (145) for Promethium (Pm), the atomic mass reflects that of the most stable isotope1, and is not the average atomic mass for all isotopes of the element. Atomic masses used on this periodic table are from the IUPAC 1995 recommendations.
Melting Point- The melting point of any element is the temperature at which the element changes from a solid to a liquid or from a liquid to a solid. Even though water is not an element, I will be using it in this example. Water freezes and ice melts at 0 °C (32 °F). Therefore, the melting point of water is 0 °C. The melting point is provided in degrees Celsius, Fahrenheit, and Kelvin. The melting point of a substance is also the freezing point.
Boiling Point- The boiling point of any element is the temperature at which it changes from a liquid to a gas or from a gas to a liquid. You probably know that water changes to steam and steam changes to water at a temperature of 100 °C (212 °F). The boiling point of water is 100 °C. Therefore, the boiling point is also the condensation point. The boiling point is provided in degrees Celsius, Fahrenheit, and Kelvin.
Number of Protons/Electrons- The number of protons/electrons in any atom is always equal to the atomic number of the atom. Each atom has a neutral charge, and since a proton has a positive charge and an electron has a negative charge, in order to achieve a neutral charge, the number of protons and electrons must equal. A particle that is not neutral (has either more or less electrons) is known as an ion.
Number of Neutrons- The number of neutrons in an atom is equal to the number of protons in an atom subtracted from the mass of the atom rounded to the nearest integer. This is true because both neutrons and protons have an atomic weight of approximately 1 AMU2 (see mass). Since atoms often have more than one isotope1, the number of neutrons listed on the element fact sheets is only valid for the most abundant isotope of any element.
For example, boron (B) has an atomic mass of 10.81 and an atomic number of 5. When you round 10.81 to the nearest integer, the result is 11. When you subtract the number of protons (equal to the atomic number) from the atomic mass, the result is 6. Therefore, the most common isotope of boron has 6 neutrons.
Classification- The classification of any element relates to its properties. Each periodic table may use different group names and classify each element a little differently. This periodic table uses 9 families:
Crystal Structure- The term 'Crystal Structure' refers to the way in which the atoms are arranged within an a substance (element). This property explains the way an element cleaves, or breaks apart physically. For example, an element with a cubic crystal structure, such as aluminum (Al), will break into cubes. Each side of the cube should have a straight edge.
Density- The density of an element refers to how closely its atoms are packed together. This is measured in grams per cubic centimeter. Take, for example, magnesium (Mg). Its density at 293 degrees Kelvin (20 degrees Celsius, 67 degrees Fahrenheit) is 1.738 g/cm3. This means that if you have a block of magnesium at room temperature (293 Kelvin), and you decide to cut a cube measuring 1 x 1 x 1 cm, the mass that you will cut will be 1.738 grams. The greater the density of an element is, the 'heavier' the element is.
Color- The color of an element refers to its physical reflection of light under normal conditions. For example, tin (Sn), will have a white color at room temperature. These properties may change if tin was heated to its melting point, where it would become a liquid, or if it was shown under a light with a color other than white.
Other Names- Some elements have more than one name or spelling. This may be caused by either local spelling or a naming dispute. For example, the element aluminum (Al) is spelled aluminum in the United States, but is spelled (and pronounced) aluminium in most otherEnglish-speaking countries, including Great Britain, Canada, and Australia.
A naming dispute has occurred between the American Chemical Society (ACS) and the International Union for Pure and Applied Chemistry (IUPAC) over elements 104-109. ACS has used the discoverer's suggested names, while IUPAC decided to leave the naming process up to a panel of 20 members. Until this naming dispute is resolved, this periodic table will use the systematic Latin names automatically assigned to newly discovered elements.
More information about the naming of heavy elements is available.
Atomic Structure
Number of Energy Levels- The number of energy levels refers to how many 'electron shells' or places where electrons can be an element has. An element with 4 shells, such as zinc (Zn), has 4 different areas where an electron is likely to be found.
Electron Arrangement- The electron arrangement of an atom refers to the number of electrons in each energy level. For example, carbon (C) has 6 electrons. Its atom arrangement shows that the six electrons are divided up into two shells, with 2 and 4 electrons, respectively.
Electron Configuration- The electron arrangement described above can be further described to include information about orbitals, shells, and more. This explanation is beyond the scope of this document, but if you are already aware of what these numbers mean, they are provided here for you.
Bohr Models- On this periodic table, Bohr models are now available for all 112 known elements. These models are designed to give some idea of how the electrons are spread over the energy levels. However, the Bohr model is now considered inaccurate among most scientists. This is because Bohr models show that electrons travel on specific paths or orbitals, a theory which has now been replaced by one that states that an electron has a greater probability of being in a certain area (or 'energy level') of the atom.
Half Lives
Half Lives- Half lives are defined as being the average time it takes for half of the atoms of a radioactive element to decay into their daughter elements. For example, carbon-14 (an isotope of carbon used for dating fossils) has a half life of 5730 years. This means that if you take a container of carbon-14, and leave it unchanged for 5730 years, about 50% of the carbon will remain as carbon-14, and the other 50% will decay to carbon-14's daughter element (nitrogen). If you wait for another 5730 years, about 25% of the container will be composed of the original carbon, and the other 75% will be atoms of nitrogen. Some elements, especially the heavier ones, have half lives of just a few milliseconds. For example, ununbium-277 (Uub) has a half-live of just 280 milliseconds. This means that in one second of ununbium's existence, 94% of it will radioactively decay into its daughter element.
Facts
Date of Discovery- The date of discovery of any element refers to the year in which is was first isolated and identified as an element. Some elements were discovered by early civilizations, and have an unknown discovery date.
Discoverer(s)- The discoverer of an element is defined as the first person to have identified the element. In more recent years, teams of scientists have been working on the identification of new elements, allowing more than one name to be put in this field.
Name Origin- The name origin of an element is the language/object/property/person that gives an element its name. Some elements have been assigned names of famous scientists, important mythological characters, or places. Other element's names come from foreign languages, such as Latin. The most recently discovered elements have a temporary, systematic name, assigned by IUPAC3.
Symbol Origin- When the chemical symbol of an element does not correspond to its name, its symbol origin is given on this periodic table. For example, the element lead has the chemical symbol 'Pb'. The symbol origin is from the Latin word 'plumbum', which means 'lead'.
Uses- Each element's most common uses, as an element or a compound containing the element, is written in this field.
Obtained from- The method of obtaining an element is also given under this section. Some elements are obtained from minerals, others are obtained from methods such as electrolysis of a mineral, while others are man-made.
MLA Format for Citing This Page
Check for os updates mac. Citing this Page Mac player for avi. - On each page, I have provided the current Modern Language Association (MLA) format for citing my web pages in reports and other works. I do not require that you use any particular format for citing these pages, but the MLA style is the most common one used in K-12 school and some colleges. To cite this page, for example, you would use:
Bentor, Yinon. Chemical Elements.com - Help.<http://www.chemicalelements.com/sup/help.html>.
(Where you see ', substitute the date you accessed the site, if it is not correct. Check your computer's clock to change this if it is not correct.) If this citation exceeds one line, you will need to use a hanging indent (indent every line but the first).More information about citing online sources using the MLA format can be found at http://www.mla.org.
1: An isotope is an atom of any element with the same number of protons and electrons as all the other atoms of this particular element, but with a different atomic mass (and number of neutrons).
2: AMU- Atomic Mass Unit(s)
3: IUPAC- International Union for Pure and Applied Chemistry
This page was created by Yinon Bentor.
Use of this web site is restricted by this site's license agreement.
Copyright © 1996-2012 Yinon Bentor. All Rights Reserved.
Why is the number of protons and electrons equal in an atom?
1 Answer
Actually the proton and electron count of an atom are equal only when the atom is neutral in charge.
The three atomic particles of an atom are the protons, which carry a positive charge, the electrons which carry a negative charge and the neutrons which have no charge. The proton number is always the same as the atomic number for the element.
The protons and neutrons are found in the nucleus of the of the atom and make up the major it of the mass of the atom. The electrons are found in orbitals surrounding the nucleus.
In order for the atom to remain electrically neutral the protons and electrons must balance each other.
Two examples would be Sodium (Na) and Chlorine (Cl)
Sodium has an atomic number of 11 and an amu of 23
Sodium has 11 protons 12 neutrons and 11 electrons.
11 protons - atomic number 11
11 + 12 = 23 the amu
Chlorine has an atomic number of 17 and an amu of 35
CHEM Chapter 4: Atoms Flashcards | Quizlet
Sodium has 17 protons 18 neutrons and 17 electrons.
17 protons - atomic number 17
17 + 18 = 35 the amu
The Number Of Neutrons In An Atom Is Equal To
Related questions