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 on: December 01, 2020, 04:00:10 AM 
Started by Mohammad umer - Last post by Mohammad umer

Radioactivity pops up fairly often in the news. For instance, you might have read about it in discussions of nuclear energy, the Fukushima reactor tragedy, or the development of nuclear weapons. It also shows up in popular culture: many superheroes’ origin stories involve radiation exposure, for instance—or, in the case of Spider-Man, a bite from a radioactive spider. But what exactly does it mean for something to be radioactive?
Radioactivity is actually a property of an atom. Radioactive atoms have unstable nuclei, and they will eventually release subatomic particles to become more stable, giving off energy—radiation—in the process. Often, elements come in both radioactive and nonradioactive versions that differ in the number of neutrons they contain. These different versions of elements are called isotopes, and small quantities of radioactive isotopes often occur in nature. For instance, a small amount of carbon exists in the atmosphere as radioactive carbon-14, and the amount of carbon-14 found in fossils allows paleontologists to determine their age.
In this article, we’ll look in more detail at the subatomic particles that different atoms contain as well as what makes an isotope radioactive.

Atomic number, atomic mass, and relative atomic mass

Atoms of each element contain a characteristic number of protons. In fact, the number of protons determines what atom we are looking at (e.g., all atoms with six protons are carbon atoms); the number of protons in an atom is called the atomic number. In contrast, the number of neutrons for a given element can vary. Forms of the same atom that differ only in their number of neutrons are called isotopes. Together, the number of protons and the number of neutrons determine an element’s mass number: mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number.
A property closely related to an atom’s mass number is its atomic mass. The atomic mass of a single atom is simply its total mass and is typically expressed in atomic mass units or amu. By definition, an atom of carbon with six neutrons, carbon-12, has an atomic mass of 12 amu. Other atoms don’t generally have round-number atomic masses for reasons that are a little beyond the scope of this article. In general, though, an atom's atomic mass will be very close to its mass number, but will have some deviation in the decimal places.
Since an element’s isotopes have different atomic masses, scientists may also determine the relative atomic mass—sometimes called the atomic weight—for an element. The relative atomic mass is an average of the atomic masses of all the different isotopes in a sample, with each isotope's contribution to the average determined by how big a fraction of the sample it makes up. The relative atomic masses given in periodic table entries—like the one for hydrogen, below—are calculated for all the naturally occurring isotopes of each element, weighted by the abundance of those isotopes on earth. Extraterrestrial objects, like asteroids or meteors, might have very different isotope abundances.

 on: November 30, 2020, 12:11:17 AM 
Started by Mohammad umer - Last post by Mohammad umer
What is an Atom?

Atom, the smallest unit that matter can be broken down into without releasing any electrically charged particles. Atoms are also the smallest unit of matter that exhibits the characteristic properties of an element. As such, the atom is the fundamental building block for chemistry.
Example: Ne, O
What is a Molecule?

A molecule can be defined as the combinations of two or more atoms which are held together by chemical bonds. A molecule is the smallest portion of a substance which showcases all the properties of the substance. On breaking down a molecule further, we see properties of the constituent elements.
Example: O2, HCl
Differences between Atoms & Molecules

Let us discuss the differences between atoms and molecules.
Atoms vs molecules

Factor   Atoms   Molecules
Definition   Most fundamental and smallest part that can exist of an element.   Two or more atoms chemically bonded together.
Example   Oxygen – OPhosphorus – P
Sulphur – S
Hydrogen – H   Oxygen – O2Phosphorus – P4
Sulphur – S8
Water – H2O
Structure   The smallest particle with properties of an element.   Combination of two or more atoms.
Stability   An atom may not always be stable in nature due to the presence of electrons in the outer shells.   Molecules are formed to attain stability.
Constituent Elements   Protons, Electrons & Neutrons   Two or more atoms of the same or different elements
Reactivity   Except for the noble elements, atoms of all elements showcase a certain level of reactivity.   Compared to a molecule, the level of reactivity is less than some valence points are filled by electrons of combined elements.

Frequently Asked Questions – FAQs

What is an atom and molecule?

The ‘simple building blocks of matter’ are known as atoms. The properties of the chemical element are the smallest constituent unit of substance. Molecules are made up of one or more atoms connected by covalent (chemical) bonds.

Is an atom considered a molecule?

The term molecule is also used for any gaseous particle in the kinetic theory of gases, irrespective of its structure. Usually, atoms and complexes related by non-covalent interactions, such as bonds of hydrogen or ionic bonds, are not called independent molecules. It is normal to have molecules as elements of matter.

What’s does atom mean?

The essential units of matter and the defining structure of elements are atoms. The name “atom” derives from the Greek word for indivisible, since atoms were once considered to be the smallest objects in the world and could not be separated. After the Big Bang, 13.7 billion years ago, atoms were formed.

Can an atom be created?

It is difficult to build or kill atoms, because they are indestructible; it is difficult to divide them into smaller pieces. This was founded upon the Law of Mass Conservation. It was later discovered that atoms are capable of separating into smaller pieces. The division, mixture, or rearrangement of atoms requires chemical reactions.

What is the best definition of atom?

An atom is a particle of matter that describes a chemical substance in a special way. A single nucleus, which is normally surrounded by one or more electrons, consists of an atom. Each electron is charged negatively. The nucleus is charged positively, and comprises one or two particles such as protons and neutrons that are relatively strong

 on: November 26, 2020, 12:03:30 AM 
Started by Mohammad umer - Last post by Mohammad umer
programme Details Of M.A Teaching Of English As A Foreign Language (TEFL)

Programme Name: M.A Teaching of English as a Foreign Language (TEFL)
The MA TEFL, which is a 30 credit hour programme and is aimed at training English language teachers, was launched in the earely 1990s. This programme, which offers courses that cover theoretical as well as practical aspects of English language teaching, can be very useful not only for those teachers who are already teaching English but also for the ones who want to teach English as a foreign or second language in future.
Admission Requirement:
Diploma in TEFL with 30 credits hours from AIOU. Candidate with 24 credit hours (04 credits) diploma TEFL are equivalent qualification will be offered admission with the condition to complete a 06 credit hours workshop as a makeup course.
Selection Process:
All eligible candidates will be granted Admission subject to fulfilling Eligibility criteria.
Duration: 2 Years
Medium of Instruction: English
Teaching Methodology:
The University allots Study Centre and Tutors for the Students to get guideline accordingly. A student has to secure passing marks in Assignments as well as in final exams to successfully complete concerned Educational Programme.
AIOU Credits Required: 30 Credit hours
Course Required: Semester: 1
3. GRAMMAR-5657
5. WORKSHOP-5663

Semester: 2
5. WORKSHOP-5663
8. THESIS-5670

Elective / Major Courses:
Workshop: compulsory
Thesis: Students have to work under the guidance of thesis supervisor appointed by the department according to the approved format.
Practical: In the workshop, the students have to present their research proposals for writing thesis.
Viva: Viva is conducted to give an opportunity to the students to defend their thesis. NOTE: Suggestions/queries may be sent to the Chairman of Department at this address: english@aiou.edu.pk

 on: November 24, 2020, 11:38:04 PM 
Started by Mohammad umer - Last post by Mohammad umer
Hi guys...
anyone to know about how can i learn TOEFL speaking test preparation need your guidance plz tell ASAP..

 on: November 24, 2020, 06:32:08 AM 
Started by BusinessSetup - Last post by BusinessSetup
I want to start a trading company in Dubai. Is anyone there can tell me the process of company formation, How much time it will take to register my company, how much capital/finance I need to setup a company in mainland/Freezone? How many Visas I can apply?
If anyone of you have some idea or you know some reliable business consultants rplease let me know. I am looking for some expert opinion.



 on: November 24, 2020, 01:58:55 AM 
Started by Mohammad umer - Last post by OwenGByrd
I have experience in data recovery. The PhotoRec program showed excellent results. This software has an intuitive user interface and high operating speed. I can also recommend R-Studio / Recuva.

They work great if your storage medium is healthy. However, if there are malfunctions on HDD / SSD (for example, bad sectors or memory controller errors), then the result can be much worse.

If your lost data is very valuable, then it is better to turn to information recovery professionals.

In the business sphere (for example, e-commerce or data centers), such issues are resolved by backup copying, creating raid arrays.

 on: November 24, 2020, 01:38:13 AM 
Started by Mohammad umer - Last post by Mohammad umer
hi guys...
i need your guidance plz tell me which is the best online courses in Pakistan for students.

 on: November 23, 2020, 04:46:16 AM 
Started by Mohammad umer - Last post by Mohammad umer
need your guidance.

 on: November 19, 2020, 04:44:49 AM 
Started by ThomasGrey25 - Last post by doylechamplin
I would really like to know more about this as I have recently created a new website and I am providing some bestessays discount code on it and I am sure this software would be helpful for me. Knowing more about this would help me with the work.

 on: November 19, 2020, 01:37:57 AM 
Started by Mohammad umer - Last post by Mohammad umer
Practicing Your Skills Is the Key to Success

Use English Every Day
Set aside time each day to communicate only in English. Listen, read, speak and write in English every chance you get.

Make notes for yourself and write down daily reminders, using new words and common expressions. Practice with emails if you can. This helps with sentence structure and vocabulary.

Listen to music, radio, television, movies and online broadcasts (if available) in English. The more you listen, the more you will understand vocabulary and expressions. Music helps you acquire the rhythm and stress patterns of spoken English. Listen closely to the words.

Reading is the best way to improve your vocabulary. English-language reading materials — newspapers, magazines, books and websites — are always available. Choose your favorites! Try some academic reading material to prepare for communicating at the university level in English.

Keep a Journal
Write down things you are doing to prepare for college and other events in your daily life. This is a great way to organize your thoughts and practice writing in English. You can track your own progress. Read it to yourself and read it out loud.

Tips for Success on Test Day

Follow directions carefully.
Relax and concentrate on each task in front of you.
Pace yourself and avoid rushing.
How to Mark Your Answers on the Answer Sheet
Use a medium-soft (No. 2 or HB) black lead pencil.
Mark only 1 answer to each question.
Mark your answer in the row with the same number as the question you are answering.
Fill in the oval space that corresponds to the answer. If you change your mind, erase your old answer and mark your new one.
Erase any unnecessary or stray marks. You cannot make corrections after time is called.

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