Which of dalton's five principles still hold true?

The explanation is given below

Explanation:

Dalton was the first who putted forward the theory about atom. he describe the properties of atoms of the element. Dalton based his theory on the law of conservation of mass and the law of constant composition.

His theory has 5 basic postulates and these five principals are still true.

1. Dalton stated that all matter composed of atoms are very small in size. these smallest unit of matter (atom) take part in chemical reaction.

2. All the atoms of an element are similar in shape, size, and other properties but different from the atoms of other element.

3. This theory states all matter is made up of atoms and atom can not be created nor destroy.

4. Law of constant composition:

According to this: atoms of different elements combine in a simple, fixed and  whole number ratio to form compound.

5. Atoms the element can combine in more than one ratio  and form two or more compounds.

The atomic theory of Dalton explained many things.

Other models are its modification and explanation. Dalton was the first who recognize difference between atom of an element compound.

Although there are some discrepancies to explain other points but these 5 points are still workable and true.

mechanics (greek   is that area of science concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment. the scientific discipline has its origins in ancient greece with the writings of aristotle and archimedes[1][2][3] (see history of classical mechanics and timeline of classical mechanics). during the early modern period, scientists such as galileo, kepler, and newton laid the foundation for what is now known as classical mechanics. it is a branch of classical physics that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light. it can also be defined as a branch of science which deals with the motion of and forces on objects. the field is yet less widely understood in terms of quantum theory.

explanation:

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-